WAR 
SERVICE 
LIBRARY 

•v 

THIS-BOOK-IS 
PROVIDED -BY 
THE-PEOPLE 

OF-THE 

UNITED-STATES 

THROUGH-THE 

AMERICAN 

LIBRARY 

ASSOCIATION 

FOR 

THE-USE-OF 
THE-SOLDIERS 
AND-SAILORS 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


The  RALPH  D.  REED  LIBRARY 


/>   ^          -^^ 

&& 


DEPARTMENT  OF  GEOLOGY 

UNIVERSITY  of  CALIFORNIA 

LOS  ANGELES,  CALIF. 


*»: 


*?l^:*>g3fc^'-i^ 


No. 


No.2. 


THE 


COMING  ICE  AGE 


BY 
C   A.   M.  TABER. 


BOSTON: 

GEO.  H.  ELLIS,  141  FRANKLIN  STREET. 
1896. 


COPYRIGHT,  1896. 
Bv  C.  A.  M.  TABER. 


QUO.  M.  ILLI*,  FXINTIX,  141   FKARKLIN    STUEIT,  BOSTON. 


78 
Til 


P  R  E  FA  C  E. 


THE  explanations  given  in  the  following  pages,  in  which  I 
have  sought  to  show  the  manner  in  which  an  ice  age  is  being 
brought  about,  is  an  extension  of  a  treatise  on  "  The  Cause  of 
Warm  and  Frigid  Periods,"  which  I  published  in  a  small 
edition  in  1894.  And,  from  the  small  number  of  copies  circu- 
lated, only  a  few  came  to  the  hands  of  persons  particularly 
interested  in  such  matter.  Yet  there  were  instances  of  its 
having  proved  of  special  interest  to  persons  celebrated  for  their 
geological  attainments,  and  also  to  instructors  in  physical  geog- 
raphy. Besides,  it  received  considerate  notice  in  some  of  the 
leading  reviews.  Being  thus  somewhat  encouraged,  and  think- 
ing that  the  subject  was  too  important  to  be  neglected,  I  have 
given  it  further  study  during  the  last  year,  and  meanwhile 
have  obtained  additional  information  from  recent  discoveries 
which  has  served  to  corroborate  my  views.  Hence  I  have  been 
able  to  be  more  explicit  in  my  explanations  in  the  present  vol- 
ume than  in  my  earlier  writings.  Still,  while  acting  as  a  pio- 
neer in  the  matter,  it  will  be  seen  that  I  have  only  attempted  to 
expose  the  main  outlines,  as  my  age  and  failing  health  will  not 
permit  me  to  enter  into  the  voluminous  details  necessary  for 
a  full  explanation.  In  order  to  show  why  my  attention  has 
been  turned  to  the  great  climatic  changes  which  have  taken 
place  during  past  ages,  and  now  threaten  the  future,  I  will  re- 
peat the  introduction  of  my  earlier  publication,  wherein  I 
wrote  that  "  the  reason  why  I  have  undertaken  to  explain  the 
causes  which  have  brought  about  the  warm  and  cold  epochs  is 
because  of  my  being  unable  to  harmonize  the  several  theories 


394727 


that  have  been  published  with  the  general  mode  of  action 
which  nature  pursues  to-day.  Having  in  the  early  part  of  my 
life  been  employed  for  a  score  of  years  in  the  whaling  service, 
during  which  time  my  sea  voyages  were  passed  in  cruising  over 
the  North  and  South  Atlantic,  and  over  the  Indian  Ocean, 
from  latitudes  north  of  the  equator  to  the  southern  shores  of 
Kerguelen  Land,  and  along  the  seas  of  Southern  Australia,  I 
also,  in  my  searching,  cruised  over  the  Pacific  Ocean  from  the 
icy  seas  south  of  Cape  Horn  to  the  northern  latitudes  of 
Alaska,  and,  from  New  Zealand  in  the  Western  Pacific  to  the 
numerous  islands  in  the  tropical  zone.  And  it  may  be  said 
that  among  the  chief  things  to  be  learned  on  such  voyages 
was  the  direction  of  the  prevailing  winds  and  surface  currents 
of  the  sea.  Thus  the  impressions  then  received  were  in  mind 
when,  in  after  years,  I  had  my  attention  drawn  to  the  several 
theories  advanced  for  explaining  the  causes  which  produced 
the  warm  and  frigid  epochs.  But,  so  far  as  my  marine  experi- 
ence goes,  such  theories  have  not  harmonized  with  nature's 
mode  of  operating  at  this  age  of  the  world.  Therefore,  I  have 
conceived  views  which,  to  my  mind,  are  more  agreeable  to  the 
simple  operations  of  nature  of  which  I  have  long  been  witness. 
Consequently,  I  have  written  several  short  essays  on  climatic 
changes  since  1880,  and  also  letters  relating  to  the  same  sub- 
ject, which  have  been  published  in  Science  aud  Scientific  Amer- 
ican. But  the  space  allowed  for  the  introduction  of  such 
matter  was  necessarily  too  limited  for  so  wide  an  explanation 
as  the  subject  required.  The  views  then  advanced  I  have 
again  repeated,  with  the  addition  of  several  facts  pertaining  to 
physical  geography,  which,  so  far  as  I  know,  have  never  before 
been  published." 

WAKEFIELD,  MASS.,  U.S.A. 
June,  1896. 


CONTENTS. 


CHAPTER  I. 

PAGE 

CAUSE  OF  COLD  AND  MILD  PERIODS, 9-36 

Traces  of  ancient  glaciers  in  temperate  zones,  9;  prevailing 
winds  the  main  cause  of  the  circulation  of  the  ocean  waters 
between  the  tropical  and  temperate  zones,  10;  general 
direction  of  prevailing  winds,  and  how,  in  connection  with 
continents,  they  circulate  the  surface  waters  of  the  sea,  11 ; 
high  and  low  sea-levels;  separation  of  antarctic  lands 
from  South  America,  12;  Captain  Larson's  discoveries  in 
antarctic  regions,  13;  how  low  lands  south  of  Cape  Horn 
were  submerged,  13;  how  the  winds  move  more  surface 
water  southward  than  northward,  14;  Dr.  Croll's  views  on 
winds  and  ocean  currents,  16;  under-currents  of  the  ocean, 
and  how  caused,  16;  Gulf  Stream  currents,  17;  antarctic 
under-currents,  18;  why  the  winds  were  able  to  force  more 
of  the  ocean  waters  southward  than  northward  at  the  close 
of  the  Tertiary  age,  19;  Mr.  Alfred  R.  Wallace's  views  on 
Tertiary  seas,  20;  how  the  Cape  Horn  channel  affects  the 
ocean  currents,  21 ;  cause  of  the  increase  of  cold  in  southern 
latitudes,  22;  how  the  Cape  Horn  channel  is  closed  during 
ice  age,  and  its  effect  on  ocean  currents  and  temperature 
of  southern  latitudes,  24;  the  melting  of  glaciers  from 
southern  lands,  27;  a  salt  sea  requisite  for  circulation  dur- 
ing ice  age,  28;  direction  of  surface  currents  in  southern 
seas,  29;  Humboldt  current,  30;  Agulhas  current,  32;  tem- 
peratureof  arctic  ice,  34;  movement  of  southern  icebergs,  35; 
glaciers  south  of  Cape  Horn,  36. 


CHAPTER  II. 

PAGE 
HOW     ICE     PERIODS     IN     THE     NORTHERN     HEMISPHERE     ARE 

BROUGHT   ABOUT, 37-54 

Northern  seas  during  Tertiary  age,  37 ;  Gulf  Stream  during  Ter- 
tiary times,  38;  the  origin  of  a  cold  period  in  the  northern 
hemisphere,  38;  remarks  on  Gulf  Stream  and  arctic  cur- 
rents, 39;  circulation  of  arctic  waters,  40;  arctic  channels 
during  ice  age,  41;  how  the  weight  of  glaciers  in  the  north- 
ern hemisphere  attracts  the  waters  of  the  southern  seas 
during  ice  age,  42;  Professor  Prestwich  on  the  submergence 
of  European  lands,  43;  the  great  Atlantic  tide  rips  the  head- 
waters of  the  Gulf  Stream,  44 ;  high  sea-level  of  Atlantic 
calm  region,  45;  tropical  Atlantic  currents,  46;  Sargasso 
Sea,  48;  arctic  and  Gulf  Stream  currents,  49;  Pacific  Ocean 
currents,  50;  slow  growth  of  an  ice  period,  52;  reduction  of 
Cape  Horn  channel,  53;  permanence  of  antarctic  glaciers 
elevated  above  the  snow-line  during  mild  periods,  54. 


CHAPTER   III. 

SPREAD  OF  GLACIERS  DURING  COLD  EPOCHS, 54-61 

Spread  of  glaciers  in  tropical  zone,  54;  Professor  Agassizon 
the  origin  of  Galapagos  Islands,  55 ;  the  bowlders  of  Hood's 
Island  and  rookery  of  Albatross,  56;  alpine  flora  of  Galap- 
agos and  tropical  America,  57;  Mr.  J.  Crawford  on  ancient 
glaciers  in  Nicaragua,  58;  Cuba  and  Republic  of  Colombia 
during  ice  age,  68 ;  destruction  of  animal  life  during  glacial 
age,  59;  temperature  of  North  Atlantic  and  Mediterranean 
Sea  during  ice  age,  60;  temperature  of  ocean  during  warm 
epochs,  61 ;  generative  age  ascribed  to  warm  eras ;  Professor 
Wright  on  pre-glacial  man,  61. 


CHAPTER   IV. 

THE    GLACIERS    OF    THE    TEMPERATE    ZONE, 62-75 

Professor  Hitchcock  on  the  early  history  of  North  America,  62; 
glacial  deposits  of  Nantucket  and  Martha's  Vineyard,  63 ; 
Professor  James  Geikie  on  the  glacial  deposits  of  Northern 
Italy,  64 ;  California  coast  ranges  the  work  of  Sierra  glaciers, 


65;  ancient  glaciers  on  the  Pacific  slope  north  of  California, 
67 ;  Professor  Geikie's  views  on  the  ancient  glaciers  in  the 
Salt  Lake  region,  68;  Colorado  Canon,  69;  the  conglomerate 
deposits  in  the  Appalachian  district,  69;  remarks  on  the 
glacial  boundaries  in  United  States  during  ice  age,  70; 
sands  of  Florida,  71 ;  ancient  ice-sheets  of  the  plains  west 
of  the  Mississippi  River,  73;  the  driftless  region  of  Wiscon- 
sin, 74;  tropical  waters  of  North  Atlantic  chilled  during  ice 
age,  75;  the  drifted  snow  of  British  America  and  Siberia 
during  ice  age,  75. 

CHAPTEK  V. 

PAGB 

REMARKS   ON   THEOBIES   ADVANCED  FOR   EXPLAINING  ICE 

PERIODS, 76-93 

Professor  Geikie  on  supposed  causes  of  the  glacial  period,  76; 
change  in  the  relative  level  of  the  land  and  sea  during 
glacial  and  post-glacial  times,  77;  submergence  of  northern 
lands  at  close  of  ice  age,  78;  the  main  cause  of  the  move- 
ment of  water  from  the  northern  seas  at  the  close  of  glacial 
age,  79;  why  the  earth  movement  hypothesis  should  be  re- 
jected, 79;  glaciers  of  Europe  and  Alaska,  80;  North  Pacific 
currents,  81;  why  the  Pacific  waters  are  growing  cool,  82; 
the  lowering  temperature  of  the  northern  seas,  83 ;  the  in- 
crease of  cold  in  Europe  and  Asia,  84 ;  falling  temperature 
of  the  Andean  region,  85;  General  Drayson's  astronomical 
discoveries  for  explaining  the  cause  of  ice  periods,  87 ;  why 
the  Gulf  Stream  was  always  confined  to  the  North  Atlantic, 
89;  the  improbability  of  the  Indian  Ocean  currents  entering 
the  arctic  seas,  90;  why  the  increase  of  glaciers  must  con- 
tinue while  the  Cape  Horn  channel  maintains  its  present 
capacity,  91;  comments  on  the  coming  ice  age,  92;  tropical 
zone  the  abode  of  man  during  ice  age,  93;  preservation  of 
the  tropical  ocean  fauna  through  the  glacial  period,  93. 


CHAPTER  I. 

CAUSE   OF   COLD   AND   MILD   PERIODS. 

IT  is  now  generally  conceded  by  those  who  have  given  the 
subject  much  attention  that  the  greater  portion  of  North  Amer- 
ica above  the  latitude  of  39°  north  to  the  shores  of  the  Arctic 
Ocean  has  been  furrowed  and  scoured  by  the  action  of  ice. 

Vast  traces  of  ancient  glaciers  are  also  found  in  Europe ;  for 
it  is  reported  that  ice-sheets  have  left  unmistakable  marks  of 
having  overrun  the  greater  part  of  the  lands  lying  between  the 
arctic  seas  and  the  latitude  of  the  Pyrenees. 

In  Asia  evidences  of  glacial  action  have  been  noticed  from 
Northern  Siberia  to  the  mountains  of  Syria. 

The  great  glaciers  of  Himalaya  have  in  times  past  attained 
gigantic  proportions.  In  Northern  China  huge  bowlders  are 
found  scattered  over  the  valleys,  and  a  long  distance  from  the 
mountains. 

The  southern  hemisphere,  in  proportion  to  the  extent  of  its 
land  surface,  shows  ample  traces  of  former  ice  action.  From 
the  latitude  of  38°  south  to  the  southern  extremity  of  the 
western  continent  there  is  said  to  be  the  clearest  evidence  of 
former  glacial  action  in  numerous  bowlders  scattered  over  the 
land. 

On  the  shores  of  the  South  Pacific,  from  the  Island  of  Chiloe 
to  Cape  Horn,  the  coast  is  fringed  with  deep  fiords,  which 
appear  to  be  channelled  out  by  ice,  like  the  fiords  of  Norway 
and  Greenland.  And  at  this  date  the  mountains  of  that 
southern  region  are  covered  with  snow,  and  the  glaciers  which 
flow  down  the  valleys  are  said  to  reach  the  tide-water  as  far 
north  as  the  latitude  of  47°  south.  The  glaciers  of  New  Zea- 


10 

land,  now  of  Alpine  proportions,  during  the  ice  age  descended 
to  the  sea,  and  channelled  the  deep  fiords  on  its  south-western 
coast ;  and  certain  traces  of  glacial  action  have  been  observed 
in  Southern  Australia,  and  also  in  the  province  of  Natal,  South 
Africa. 

Kerguelen  Land  is  pierced  with  deep,  narrow  fiords,  which 
have  the  appearance  of  having  been  the  work  of  ancient 
glaciers. 

The  lands  south  of  the  antarctic  circle  are  to-day  supposed  to 
be  covered  by  an  ice-sheet,  of  which  the  great  ice  barrier  sur- 
rounding that  region  furnishes  ample  proof. 

While  impressed  with  the  above  reports  of  the  work  of 
ancient  glaciers,  in  connectiou  with  my  own  observations  along 
the  shores  of  the  several  oceans,  I  have  been  led  to  seek  for  the 
physical  causes  which  brought  about  the  great  climatic  changes 
of  past  geological  ages.  And,  while  having  the  subject  under 
consideration,  I  have  had  my  attention  directed  to  the  manner 
in  which  the  great  prevailing  winds  in  connection  with  conti- 
nental lands  are  able  to  move  the  heated  surface  waters  of  the 
tropical  oceans  into  the  colder  zones,  and  also  transfer  the  cold 
waters  of  the  higher  latitudes  into  the  tropical  zones. 

And  it  is  through  this  grand  movement  of  the  ocean  waters 
that  we  are  enabled  to  account  for  the  difference  in  the  tem- 
perature of  places  now  lying  in  the  same  parallels  of  latitude. 

The  natural  methods  for  conveying  tropical  heat  into  the 
higher  latitudes,  and  also  for  excluding  it  therefrom,  are  so 
simple  and  efficient  that  on  due  consideration  we  are  able  to 
conceive  how  epochs  possessing  mild  climates  have  been  suc- 
ceeded by  periods  of  frigidity. 

It  has  been  admitted  by  several  writers  on  climatic  changes 
•  that,  should  the  tropical  surface  waters  of  the  ocean  be  moved 
into  the  high  latitudes  in  large  volume,  thus  adding  their 
warmth  to  the  heat  imparted  by  the  sun,  such  combined  heat 
would  cause  a  mild  climate.  And  it  has  been  estimated  that 
the  amount  of  equatorial  heat  moved  into  the  temperate  and 


11 

polar  regions  of  the  northern  hemisphere  by  the  Gulf  Stream 
alone  is  equal  to  one-fourth  of  all  the  heat  received  from  the 
sun  by  the  North  Atlantic  from  the  tropic  of  Cancer  to  the 
arctic  circle.  Still,  it  appears  to  me,  while  viewing  the  subject 
from  a  marine  standpoint,  that  the  explainers  of  climatic 
changes  have  never  fully  comprehended  the  manner  in  which 
the  surface  waters  of  the  ocean  are  moved  from  the  tropics  into 
the  high  latitudes,  and  returned  from  the  high  latitudes  to  the 
tropics.  Consequently,  they  have  neglected  necessary  and  effi- 
cient natural  agents  in  their  explanatory  theories,  and  with 
much  learning  and  ingenuity  have  laboriously  sought  to  show 
how  great  changes  of  climate  could  be  brought  about  through 
other  causes. 

But  when  we  notice  the  simple  methods  employed  by  nature 
to-day  for  transferring  the  heat  of  the  tropics  into  the  higher 
latitudes,  and  also  the  manner  of  excluding  such  heat  there- 
from, they  appear  to  afford  an  explanation  for  the  great 
changes  of  climate  which  have  taken  place  during  past  ages ; 
for  it  appears  that  the  natural  manner  of  proceeding  by  which 
heat  is  moved  from  the  torrid  zone  into  the  high  latitudes 
sufficient  to  cause  a  mild  climate  is  through  the  ocean  currents 
which  are  constantly  set  in  motion  by  the  great  prevailing 
winds  of  the  globe.  These  winds,  as  is  well  known,  blow 
mostly  from  the  east  toward  the  west  in  the  tropics,  and  from 
the  west  toward  the  east  in  the  high  latitudes. 

This  counter-movement  of  the  winds,  in  connection  with  a 
continent  extending  both  northward  and  southward  from  the 
equator  over  many  degrees  of  latitude,  such  as  obtains  on  the 
western  continent,  is  abundantly  able  to  create  extensive  de- 
pressions and  elevations  on  the  ocean's  surface,  and  thus  cause 
vast  streams  of  water  to  move  by  gravity  from  the  high  sea- 
levels  to  the  low  sea-levels ;  and  in  this  way  the  tropical  waters 
have  been  moved  during  past  ages,  and  to  a  considerable  extent 
are  now  moved  far  into  the  northern  and  southern  seas. 

This  transfer  of  the  ocean  waters  is  the  main  cause  of  a  tern- 


12 

perate  climate  being  enjoyed  by  countries  situated  in  the  high 
latitudes  at  this  age. 

But,  in  order  that  the  tropical  currents  should  be  able  to  flow 
into  the  high  latitudes,  in  quantities  sufficient  to  cause  all  lands 
and  seas  situated  in  such  latitudes  to  enjoy  a  mild  climate,  it 
would  be  necessary  that  the  land  should  extend  unbroken,  or 
nearly  so,  from  the  arctic  to  the  antarctic  circles.  Thus,  with 
a  continent  of  such  vast  extent,  the  westerly  winds  would  blow 
the  surface  waters  of  the  ocean  away  from  the  eastern  shores 
in  the  high  latitudes,  and  so  cause  extensive  low  sea-levels ; 
while  the  easterly  winds  of  the  torrid  zone  would  heap  the 
surface  waters  of  the  ocean  against  the  eastern  tropical  shores 
of  the  continent.  Consequently,  the  warm  waters  of  the  trop- 
ical high  sea-level  would  be  moved  by  gravity  to  the  low  sea- 
levels  of  the  high  latitudes,  even  to  the  arctic  and  antarctic 
regions,  and  thus  afford  them  a  mild  climate.  In  this  way  we 
account  for  the  mild  climate  enjoyed  on  lands  and  seas  within 
the  high  latitudes  during  the  warm  epochs  anterior  to  the 
glacial  periods. 

As  the  western  continent  is  the  only  land  that  extends  un- 
broken from  the  equator  to  the  cold  latitudes  of  both  hemi- 
spheres, thus  affording  an  opportunity  for  the  prevailing  winds 
to  move  the  tropical  waters  into  the  high  latitudes,  I  will  call 
attention  to  that  portion  of  the  continent  which  extends  far 
southward  into  the  southern  ocean,  where  the  winds  and  ocean 
currents  have  the  greatest  range  and  power  to  affect  the  cli- 
mate on  different  parts  of  the  globe.  Here  we  see  South 
America  separated  from  the  antarctic  continent  by  a  wide 
channel  of  deep  water,  where  the  westerly  winds  blow  with 
great  force.  The  space  now  covered  by  this  interesting  chan- 
nel, owing  to  its  being  situated  in  the  high  southern  latitudes, 
must  have  been  occupied  by  a  channel  of  comparatively  small 
capacity,  or  else  an  isthmus  of  low  land  uniting  the  southern 
portion  of  South  America  with  the  antarctic  continent  during 
the  warm  epochs  when  the  beds  of  the  ancient  seas  of  the 


13 

northern  hemisphere  contained  a  considerable  portion  of  the 
water  now  swelling  the  southern  ocean. 

Therefore,  the  obstructions  which  separated  the  Pacific 
Ocean  from  the  South  Atlantic  furnished  opportunity  for  the 
westerly  winds  to  force  the  surface  waters  of  the  sea  away 
from  the  leeward  side  of  such  obstructions,  causing  a  vast  low 
sea-level,  sufficient  to  attract  the  tropical  waters  heaped  against 
Brazil  by  the  trade  winds  into  the  southern  seas  in  adequate 
quantity  to  cause  a  mild  climate  throughout  the  antarctic 
regions  through  long  periods  of  time. 

Recent  discoveries  have  proved  that  these  high  southern  lati- 
tudes have  been  subject  to  great  changes  of  climate.  Accord- 
ing to  the  reports  from  the  Dundee  whalers,  while  searching 
for  seal  in  the  icy  seas  that  surround  the  South  Shetlands,  they 
met  with  the  Norwegian  ship  "  Jason,"  Captain  Larsen,  who 
had  traced  the  eastern  shore  of  Graham  Land  to  68°  south  lati- 
tude, noting  two  active  volcanoes. 

The  same  mariner  brought  from  Seymour  Island  fossil 
shells  and  coniferous  wood  of  the  Tertiary  epoch. 

These  furnish  sufficient  evidence  to  show  that  a  warmer 
climate  once  prevailed  there. 

At  the  commencement  of  the  glacial  age  the  obstructions 
which  separated  the  South  Pacific  from  the  South  Atlantic  had 
become  deeply  submerged  by  the  sea,  which  may  have  been 
caused  by  a  tendency  of  the  ocean's  waters  to  move  southward 
or  by  a  comparative  small  movement  in  the  earth's  crust.  But, 
on  account  of  the  stability  of  the  crust  of  the  earth  during 
times  so  late  as  the  glacial  epochs,  the  submergence  of  this 
southern  region  was  probably  owing  to  the  movement  of  the 
ocean's  waters  from  the  northern  hemisphere  into  the  southern 
hemisphere,  which  appears  to  have  been  brought  about  mostly 
through  the  agency  of  the  great  prevailing  winds  ;  for  it  seems 
to  have  happened  that  the  prevailing  winds  on  account  of  the 
disposition  of  the  lands  and  seas  were  able  to  move  more  of  the 
ocean  waters  southward  than  they  moved  northward  during 


14 

the  age  preceding  the  glacial  periods.  The  waters  thus  slowly 
and  gradually  forced  into  the  high  southern  latitudes  must 
have  deprived  the  northern  hemisphere  of  their  heaviness,  and 
added  their  weight  to  the  southern  hemisphere.  Therefore, 
the  waters  moved  southward  could  not  all  be  returned  to  the 
seas  of  the  northern  hemisphere  by  gravity,  for  the  reason  that 
the  earth's  centre  of  attraction  would  change  in  accordance 
with  the  weight  of  water  moved  from  the  northern  hemisphere 
into  the  southern.  It  will  thus  be  seen  that,  while  the  north- 
ern seas  were  drained  or  became  shallow,  the  augmented  south- 
ern oceans  deeply  submerged  the  region  south  of  Cape  Horn, 
thus  widely  separating  the  western  continent  from  the  antarc- 
tic lands. 

Although  the  south-east  trade  winds  on  the  eastern  sides  of 
the  Atlantic  and  Pacific  Oceans  extend  further  northward  than 
the  north-east  trade  winds  extend  southward,  owing  to  the 
heated  tropical  shores  north  of  the  equator  being  more  exten- 
sive than  such  lands  south  of  the  equator,  still,  on  account  of 
the  general  weakness  of  the  south-east  trade  winds  at  the  equa- 
tor, and  also  because  of  the  obstructing  northern  lands,  they 
have  during  remote  times,  and  at  this  age,  been  largely  pre- 
vented from  impelling  the  surface  waters  of  the  sea  into  the 
northern  latitudes  in  opposition  to  the  brisk  north-east  trades. 
Furthermore,  on  account  of  the  widening  of  the  oceans  as  they 
extend  southward,  the  surface  currents  setting  in  the  latter 
direction  have  more  broad  and  easy  passages  than  the  great 
currents  setting  northward. 

Moreover,  the  great  currents  setting  southward  on  the  west- 
ern sides  of  the  oceans  south  of  the  equator  are  also  much 
assisted  during  the  southern  summer  months  by  the  strong 
north-east  monsoons  which  prevail  along  the  east  coast  of 
equatorial  Africa  and  the  east  coast  of  South  America  as  far 
as  the  latitude  of  30°  south. 

The  South  African  current  is  impelled  northward  by  the 
trade  winds  down  the  south-western  coast  of  Africa ;  but  it  is 


15 

debarred  from  entering  the  northern  latitudes  by  the  Guinea 
currents,  and  so  turned  away  into  the  south  equatorial  current 
which  flows  into  the  Brazilian  stream. 

The  Gulf  Stream  is  much  obstructed  in  its  northern 
movement  by  the  narrow  Florida  channel  and  the  opposing 
arctic  currents,  and  also  by  the  trend  of  the  North  American 
coast  eastward ;  while  its  return  current  on  the  eastern  side 
of  the  Atlantic  has  a  much  less  obstructed  passage  in  its  south- 
ern movement,  and,  while  on  its  way  past  the  Azores  and 
Madeira  Islands,  is  largely  assisted  by  the  prevailing  winds. 

The  Brazil  current,  with  the  impelling  force  of  a  strong 
north-east  monsoon  during  the  summer  season,  has  no  obstruc- 
tion whatever  in  its  southern  passage  until  it  meets  with  an  off- 
shoot from  the  great  drift  current  of  the  southern  ocean. 

And  the  same  favorable  conditions  are  obtained  by  the  great 
currents  setting  southward  on  the  western  sides  of  the  South 
Pacific  while  on  their  way  to  the  low  sea-levels  east  of  Southern 
Australia  and  Xew  Zealand.  That  portion  of  the  equatorial 
stream  of  the  Pacific  which  continues  west  across  the  Indian 
Ocean  finds  no  open  passage  to  the  northern  seas.  Conse- 
quently, it  turns  south  along  the  east  coast  of  Africa  into  the 
southern  seas. 

Therefore,  this  current,  in  connection  with  the  great  currents 
setting  southward  east  of  Australia,  offsets  the  great  Humboldt 
current  setting  north  along  the  coast  of  Peru. 

In  the  Xorth  Pacific  the  Japanese  current  setting  northward 
is  obstructed  by  the  narrowing  of  the  ocean ;  while  its  return 
current  on  the  American  side  has  a  constantly  widening  ocean 
on  its  passage  southward,  and  also  favorable  winds  to  impel  the 
surface  waters  toward  the  equator.  Still,  with  all  the  facilities 
above  mentioned  for  the  movement  of  the  ocean  waters  into  the 
southern  latitudes,  it  is  probable  that  since  the  shallow  seas  of 
the  northern  hemisphere  were  drained,  or  much  diminished, 
the  prevailing  winds  have  not  possessed  sufficient  force  to 
further  augment  the  southern  seas,  because  of  the  superior 


16 

weight  of  the  land  in  the  northern  hemisphere  compared  with 
the  lands  south  of  the  equator. 

It  will  appear  to  those  who  attribute  the  rotation  of  the 
earth  as  being  the  main  cause  of  ocean  currents  that  I  am  too 
much  given  over  to  the  wind  theory.  But  I  have  reason  to 
believe,  as  Dr.  Croll  has  asserted,  that  "the  winds  are  the 
principal  cause  of  the  ocean  currents,  and  are  not  due  to  the 
trade  winds  alone,  but  to  the  general  impulse  of  the  prevailing 
winds  of  the  globe." 

Dr.  Croll  also  declares  that  "  all  of  the  principal  currents  of 
the  globe  are  moving  in  the  exact  direction  which  they  ought 
to  move,  assuming  the  winds  to  be  the  sole  impelling  cause." 

Those  who  think  that  the  rotation  of  the  earth  is  the  real 
cause  of  the  movement  of  the  great  surface  currents  of  the  sea 
should  explain  in  some  reasonable  way  why  the  Agulhas  cur- 
rent turns  west  into  the  Atlantic  from  the  Mozambique  stream, 
and  why  the  Guinea  current  turns  to  the  east  from  the  main 
tropical  current  of  the  North  Atlantic ;  for  it  seems  that  these 
two  great  currents  move  in  direct  opposition  to  the  rotation 
theory,  while  at  the  same  time  many  things  go  to  show  that 
they  receive  their  motion  from  the  winds.  This  view  of  the 
question  will  receive  further  attention  in  succeeding  pages. 

It  is  the  opinion  of  some  writers  that  a  difference  of  temper- 
ature and  density  between  the  waters  of  the  polar  latitudes 
and  the  torrid  zone  is  the  principal  cause  of  the  movement  of 
the  surface  waters  of  the  ocean  from  the  equatorial  latitudes 
toward  the  polar  seas,  and  so  returned  in  under-currents  ;  and 
this  is  a  favorable  factor  for  assisting  the  winds  on  some  parts  of 
the  sea,  especially  in  aiding  the  Brazil  current  in  moving  the 
surface  waters  from  the  high  sea-levels  abreast  Brazil,  and  the 
equatorial  calm  belt  of  the  Atlantic  into  the  southern  ocean, 
and  also  for  favoring  the  surface  currents  setting  southward  on 
the  western  sides  of  the  South  Pacific  and  Indian  Oceans. 

Yet,  whatever  gravitating  force  it  may  possess  for  assisting 
the  above-named  currents,  it  would  also  act  against  the  impel- 


17 

ling  force  of  the  trade  winds,  while  they  were  drifting  the  sur- 
face waters  northward  toward  the  equator  on  the  eastern  sides 
of  the  several  oceans,  and  also  to  retard  the  returning  surface 
currents,  while  being  drifted  by  the  winds  southward  on  the 
eastern  sides  of  the  North  Atlantic  and  North  Pacific.  There- 
fore, while  it  would  seem  to  favor  the  winds  in  their  work  on 
the  one  hand,  it  woald  act  as  an  opposing  agent  on  other  parts 
of  the  ocean.  Still,  the  difference  of  temperature  between  the 
tropical  and  antarctic  seas  probably  does  act  in  opposition  to 
the  wide  and  brisk  trade  winds  on  the  eastern  sides  of  the  great 
oceans  south  of  the  equator,  and  so  prevents  their  impelling 
the  surface  waters  northward  to  a  great  extent ;  and  this  seems 
to  be  one  great  cause  of  there  being  less  surface  water  moved 
northward  than  southward  over  the  greatest  oceans  of  the 
globe. 

The  theory  that  the  difference  of  density  caused  by  the  dif- 
ference of  temperature  between  the  polar  seas  and  the  equato- 
rial oceans  made  under-currents  to  flow  from  the  polar  lati- 
tudes, and  meet  in  the  equatorial  seas,  can  only  be  carried  on 
in  the  Atlantic  Ocean,  and  in  a  comparatively  less  perfect  way 
in  the  Pacific  Ocean,  and  not  at  all  in  the  Indian  Ocean. 

The  North  Atlantic  being  open  to  the  Arctic  Ocean,  a  por- 
tion of  the  Gulf  Stream  waters  that  enter  it  from  the  north- 
west of  Europe  do  sink  and  return  southward  in  under-cur- 
rents ;  and  the  cold  waters  which  pass  down  the  east  and  west 
coast  of  Greenland  also  sink  under  the  Gulf  Stream  while  on 
their  southern  movement.  The  meeting  of  these  arctic  currents 
with  the  cold  under-currents  from  the  antarctic  seas  in  the 
tropical  zone  is  probably  one  cause  of  their  cold  waters  rising 
near  the  surface  of  the  sea  in  the  torrid  latitudes  of  the  Atlan- 
tic ;  and  the  same  conditions  probably  obtain  in  a  somewhat 
less  degree  in  the  Pacific  Ocean. 

Yet  it  appears  that  the  cold  waters  of  the  Antarctic  occupy 
the  largest  space  in  the  tropical  zone,  even  in  the  North  Atlan- 
tic. Dr.  Carpenter,  in  his  lectures  on  Ocean  Currents,  speaks  of 


18 

meeting  with  antarctic  water  so  far  north  as  the  latitudes  of  the 
West  India  Islands ;  and  he  also  says  that  all  of  the  Pacific 
Ocean  at  its  depths  is  supplied  from  the  Antarctic  Ocean,  as  are 
the  cold  under-waters  of  the  tropical  Indian  Ocean,  which  ex- 
tend over  twenty  degrees  north  of  the  equator. 

Thus,  from  what  we  can  learn  of  the  antarctic  under-currents, 
they  seem  to  show  that  they  are  not  wholly  attracted  north- 
ward on  account  of  the  difference  of  temperature  between  the 
antarctic  and  the  tropical  oceans,  but  partly  because  of  more 
surface  water  being  moved  southward  by  the  prevailing  winds 
than  they  are  able  to  move  northward. 

And  it  appears  that,  if  through  the  winds,  combined  with 
the  difference  of  temperature  between  the  antarctic  seas  and  the 
equatorial  waters,  and  also  because  of  the  oceans  widening 
toward  the  south,  more  surface  water  is  being  carried  south- 
ward than  northward,  the  waters  of  the  under-currents  so 
caused  must  rise  toward  the  surface  in  the  latitudes  from 
which  they  were  first  removed.  Having  called  attention  to  the 
fact  that  the  prevailing  winds  are  not  able  at  this  date  to  aug- 
ment the  southern  ocean  waters  from  the  scanty  northern  seas, 
because  of  the  preponderance  of  northern  lands,  still  there  is 
reason  to  believe  that  even  now,  owing  to  the  form  of  conti- 
nents and  oceans,  and  the  attraction  of  the  tropical  surface 
waters  into  the  Antarctic  Ocean  because  of  the  difference  of 
density  between  the  warm  and  cold  seas,  the  prevailing  winds 
of  this  age  are  able  to  force  more  of  the  surface  waters  of  the 
sea  southward  than  they  force  northward;  but,  owing  to  the 
superior  weight  of  the  land  in  the  northern  hemisphere,  the  sur- 
plus surface  water  forced  into  the  southern  seas  is  returned  by 
gravity  after  being  cooled  by  the  antarctic  ice,  and  so  adding  to 
the  deep  under-currents  which  flow  with  a  sluggish  movement 
over  the  bottom  of  the  sea  into  the  tropical  and  northern  tem- 
perate latitudes.  And  in  this  way  the  northern  oceans  are 
maintained  at  their  present  sea-level. 

The  cold    under-currents    are    probably  assisted   in    their 


19 

northern  movement  by  whatever  difference  there  may  be  in  the 
density  of  the  antarctic  waters  over  the  bottom  waters  of  the 
equatorial  seas.  But,  as  such  currents  extend  into  the  northern 
tropical  latitudes  of  the  northern  hemisphere,  it  seems  that  the 
winds  are  the  main  cause  of  the  under-currents  which  carry  so 
much  antarctic  cold  into  the  northern  tropical  seas,  because  the 
winds  have  forced  an  undue  proportion  of  ocean  surface  water 
southward,  to  be  attracted  northward  in  under-currents  by  the 
preponderating  northern  lands. 

Yet,  notwithstanding  the  superior  weight  of  land  in  the 
northern  hemisphere,  it  appears  that  there  have  been  periods 
when  there  was  somewhat  more  water  in  the  oceaus  of  the 
southern  hemisphere  than  now;  for  it  is  reported  that  a  por- 
tion of  the  low  lands  of  Australia  show  traces  of  having  been 
submerged  during  late  geological  times. 

This  may  have  happened  through  an  increased  weight  in  the 
antarctic  glaciers,  which  have  in  past  ages,  and  probably  may  in 
future  epochs,  cause  more  of  the  ocean  waters  to  be  attracted 
southward  than  now  obtains.  But  it  is  probable  that  an  in- 
crease of  southern  ice  would  be  largely  counterbalanced  by  the 
accumulation  of  ice  on  northern  lands. 

Yet  it  appears  certain  that  since  the  Tertiary  epoch  the 
waters  of  vast  shallow  seas  have  been  moved  from  the  northern 
hemisphere  into  the  southern.  The  dry  beds  of  the  ancient 
northern  seas  encourage  this  opinion,  while  the  comparatively 
small  area  of  southern  lands  serves  to  support  such  views. 

Still,  during  the  ages  prior  to  the  glacial  periods,  while  the 
low  lands  of  the  northern  hemisphere  were  covered  by  the  sea, 
the  wide  shoal  channels  which  submerged  the  lower  portion  of 
North  America  afforded  convenient  passages  for  the  surface 
waters  of  the  ocean  in  their  northern  movement,  and  so  pre- 
vented the  oceans  of  the  southern  hemisphere  from  gaining 
undue  preponderance. 

Hence  long  geological  ages  passed  away  before  the  winds 
were  able  to  force  more  of  the  ocean  waters  southward  than  they 


20 

could  move  northward,  and  thus  augment  the  southern  ocean 
from  the  waters  of  the  northern  seas.  But  the  slow  growth  of 
such  immense  marine  deposits  in  the  shallow  seas  as  are  found 
in  the  Florida  Peninsula  and  other  portions  of  that  region  was 
at  length  sufficient  to  greatly  obstruct  the  passage  of  the  Gulf 
currents  in  their  northern  movement,  and  thus  cause  conditions 
which  enabled  the  winds  to  force  more  of  the  ocean  waters 
southward  than  they  could  move  northward  after  the  close  of 
the  Tertiary  epoch. 

Mr.  Alfred  R.  Wallace  says  in  "  Island  Life  "  that  the  seas 
in  the  northern  hemisphere  during  the  Tertiary  period  covered 
a  much  larger  area  than  now,  and  extended  across  .Central 
Europe  and  portions  of  Western  Asia,  and  the  Arctic  Ocean 
was  enlarged. 

As  it  is  not  likely  that  any  portion  of  the  waters  of  the  sea 
have  been  absorbed  by  the  earth  during  the  late  epochs  in  the 
world's  history,  therefore  the  ocean  waters  have  not  diminished 
except  during  cold  periods,  when  the  water  evaporated  from 
the  sea  was  converted  into  ice,  and,  eventually,  again  returned 
to  the  sea. 

Thus  it  necessarily  follows  that,  when  the  seas  of  the 
northern  hemisphere  contained  a  much  larger  portion  of  the 
waters  of  the  globe  than  at  this  age,  the  seas  of  the  southern 
hemisphere  must  have  contained  proportionally  less.  Conse- 
quently, during  such  times  a  portion  of  the  shoal  seas  of  the 
high  southern  latitudes  must  have  been  dry  land.  Therefore, 
this  must  have  been  the  condition  of  the  shallow  sea  basins  in 
the  region  of  Cape  Horn. 

Mr.  Wallace  also  says  that  "  many  peculiarities  in  the  distri- 
bution of  plants  and  some  groups  of  animals  in  the  southern 
hemisphere  render  it  almost  certain  that  there  has  sometimes 
been  a  greater  extension  of  antarctic  lands  during  Tertiary 
times." 

And  he  also  asserts  that  the  great  ocean  basins  have  not 
changed,  and  that  the  form  of  continents  has  been  permanent. 


21 

It  will  thus  be  seen  that  it  was  through  the  movement  of  the 
ocean's  waters  southward  that  the  low  lands  south  of  Cape 
Horn  were  covered  with  water  previous  to  the  frigid  periods, 
and  so  caused  the  wide  separation  between  the  western  conti- 
nent and  the  antarctic  lands. 

The  Cape  Horn  channel  thus  enlarged,  the  continuous 
mildness  of  the  high  southern  latitudes  which  possessed  the 
earlier  ages  came  to  an  end,  and  gave  place  to  alternate  epochs 
of  frigid  and  mild  weather.  For  it  appears  that  it  is  owing  to 
the  creation  or  enlargement  of  the  Cape  Horn  channel  that  it  is 
possible  for  frigid  periods  to  be  brought  about,  for  the  reason 
that  its  enlarged  space  of  water  prevents  the  westerly  winds 
from  maintaining  a  great  low  sea-level  in  the  higher  latitudes 
of  the  southern  ocean ;  for,  whenever  the  capacity  of  the  Cape 
Horn  channel  is  enlarged,  the  westerly  winds,  instead  of 
maintaining  a  low  sea-level  on  the  South  Atlantic,  employ 
their  force  in  impelling  the  surface  water  of  the  southern  seas 
around  the  globe.  And  this  work  the  strong  westerly  winds 
of  the  high  southern  latitudes  have  always  accomplished  when- 
ever the  Cape  Horn  channel  was  widely  open,  and  this  is  what 
the  winds  are  doing  at  this  date. 

Therefore,  such  waters  of  the  torrid  zone  as  are  moved 
southward  from  their  high  sea-level,  caused  by  the  trade  winds 
abreast  the  Brazilian  coast,  are  largely  turned  away  from  the 
high  southern  latitudes.  It  is  true,  even  with  an  enlarged 
Cape  Horn  channel,  they  can  always  flow  along  the  South 
American  coast  to  an  inferior  low  sea-level,  caused  by  the 
westerly  winds  blowing  the  surface  waters  of  the  sea  away 
from  the  coast  of  Argentine  and  Patagonia;  but  on  gaining 
that  region  they  meet  the  cold  ice-bearing  currents  which  turn 
away  east  of  Cape  Horn  from  the  great  southern  drift  current 
to  gain  the  same  low  sea-level  which  attracts  the  Brazil  water. 
Consequently,  the  ice-bearing  currents  from  the  south,  which 
branch  off  from  the  great  southern  drift  current,  are  able  to 
largely  turn  away  the  warm  Brazil  current  from  the  higher 


22 

southern  latitudes ;  and,  furthermore,  the  great  southern  drift 
current  which  passes  through  the  Cape  Horn  channel,  and  so 
onward  around  the  globe,  also  partly  turns  away  the  Mozam- 
bique current  as  well  as  the  East  Australian  current,  and  so 
largely  prevents  their  waters  from  warming  the  southern  seas. 

Therefore,  it  is  evident  that,  whenever  the  Cape  Horn 
channel  obtains  sufficient  capacity  to  give  an  independent 
circulation  to  the  southern  ocean,  the  conditions  are  favorable 
for  the  increase  of  cold  in  the  southern  latitudes.  For  it  is 
because  of  the  large  exclusion  of  the  tropical  waters  from  the 
southern  seas  that  ice-sheets  have  been  able  to  form  in  early 
periods  and  in  later  epochs  on  the  antarctic  lands,  and  store 
away  the  annual  frosts  for  thousands  of  years,  and  at  the 
same  time  furnish  icebergs  sufficient  to  chill  the  waters  of 
the  southern  temperate  oceans,  and  consequently  make  cold 
such  of  the  surface  waters  of  the  sea  as  are  forced  into  the 
southern  latitudes  by  the  winds  in  surface  currents,  and 
so  returned  to  warmer  seas  in  cold  under-currents,  and  thus 
with  such  frigid  combinations  bring  about  cold  periods. 

Thus  it  appears,  as  I  have  previously  shown,  that  it  is  owing 
partly  to  there  being  more  of  the  surface  waters  of  the  sea 
forced  southward  by  the  prevailing  winds  than  they  impel 
northward  that  the  cold  under-currents  are  maintained  ;  but  it 
also  requires  an  independent  circulation  of  the  southern  ocean, 
such  as  I  have  pointed  out,  to  cool  its  surface  waters  before 
they  can  sink  and  form  cold  under-currents. 

And  there  is  reason  to  believe  that  such  cold  under-currents 
are  more  efficient  in  lowering  the  temperature  of  the  temperate 
and  tropical  oceans  than  even  the  icebergs  which  such  under- 
currents move  into  the  temperate  seas.  And,  when  it  is  con- 
sidered that  the  cold  antarctic  under-currents  fill  the  depths  of 
the  Pacific  and  Indian  Oceans  in  the  northern  hemisphere,  and 
also  largely  the  tropical  depths  of  the  North  Atlantic,  I  am  led 
to  believe  that  the  frigid  conditions  of  the  ice  age  were  concur- 
rent in  the  northern  and  southern  hemispheres.  The  main  rea- 
sons for  such  belief  I  will  explain  in  the  following  chapter. 


23 

After  the  foregoing  explanations,  showing  how  frigid  periods 
are  brought  about  through  the  independent  circulation  of  the 
southern  ocean  surface  waters,  it  is  evident  that,  whenever 
through  a  slow  natural  process  the  Cape  Horn  channel  is  closed, 
a  great  change  is  wrought  in  the  circulation  of  the  southern 
ocean. 

For  instead  of  the  westerly  winds  blowing  the  surface  waters 
of  the  southern  seas  constantly  around  the  globe,  and  so  turn- 
ing away  and  preventing  the  entrance  of  the  tropical  currents 
into  the  high  southern  latitudes,  the  strong  westerly  winds, 
whenever  the  Cape  Horn  channel  is  closed  or  greatly  obstructed, 
would  blow  the  surface  waters  away  from  the  Atlantic  side  of 
the  closed  channel,  and  so  cause  a  great  low  sea-level,  sufficient 
to  attract  the  ocean  waters  of  the  tropical  high  sea-level  abreast 
Brazil  well  into  the  southern  seas.  Therefore,  it  is  important 
to  trace  nature's  slow  methods  of  closing  the  wide  Cape  Horn 
channel  at  the  perfection  of  an  ice  age. 

In  my  previous  explanations  on  the  subject  I  have  thought 
that,  should  the  southern  seas  have  remained  at  or  near  the 
same  sea-level  as  now,  through  an  ice  period  brought  about 
in  the  manner  I  have  described,  ice-sheets  would  accumulate 
on  the  antarctic  continent,  and  also  on  the  southern  lands  of 
South  America,  sufficient  to  flow  out  into  the  sea  and  close  the 
Cape  Horn  channel. 

But  further  consideration  shows  the  impossibility  of  the 
southern  seas  having  maintained  their  present  sea-level  during 
the  growth  of  frigid  epochs  which  have  left  such  ample  traces 
of  glaciers  having  extended  widely  over  the  lands  of  the  high 
latitudes  of  both  the  northern  and  southern  hemispheres.  For 
it  appears  that  the  larger  areas  of  land  in  the  northern  lati- 
tudes, embracing  wide  continents  and  large  islands,  must,  dur- 
ing the  growth  of  a  frigid  age,  have  increased  the  spread  of 
glaciers  many  times  greater  in  extent  than  could  be  obtained 
on  the  smaller  lands  of  the  high  latitudes  of  the  southern 
hemisphere. 


24 

For  it  is  evident  that  the  water  evaporated  from  the  sea  and 
deposited  in  snow  on  the  large  continents  and  islands  of  the 
high  northern  latitudes  during  the  growth  of  an  ice  period 
would,  while  thus  diminishing  the  ocean  waters,  greatly  in- 
crease the  weight  of  northern  lands.  Therefore,  the  waters  of 
the  diminishing  seas  of  the  southern  latitudes  would  be  at- 
tracted into  the  northern  oceans  in  opposition  to  the  prevailing 
winds. 

Thus  it  appears  that  the  Cape  Horn  channel  would  be  too 
much  reduced  at  the  perfection  of  an  ice  age  to  afford  an  in- 
dependent circulation  for  the  southern  ocean,  even  without 
being  filled  by  glaciers  to  the  extent  I  have  pointed  out  in  pre- 
vious essays.  Still,  to  whatever  dimensions  the  Cape  Horn 
channel  might  be  reduced  at  the  perfection  of  a  frigid  period, 
the  enlarged  shores  bordering  its  diminished  waters  would  be 
covered  by  heavy  glaciers  that  would  flow  into  the  shrunken 
strait,  and  so  close  it  effectually.  Thus  the  reduction  of  the 
Cape  Horn  channel  during  the  advance  of  an  ice  age  seems,  on 
close  consideration,  to  be  a  simple  operation  of  nature,  which 
in  the  normal  course  of  events  must  have  taken  place. 

As  the  closing  of  the  Cape  Horn  channel  has  been  considered 
by  reviewers  the  weak  and  questionable  point  in  preventing 
my  views  from  gaining  acceptance,  it  becomes  necessary  to  be 
explicit  concerning  the  manner  in  which  the  Cape  Horn  chan- 
nel has  in  past  ages  been  obstructed. 

According  to  the  charts  prepared  by  John  James  Wild,  the 
middle  portion  of  the  strait  is  represented  as  being  over  a 
thousand  fathoms  in  depth ;  but,  as  far  as  I  know,  its  true  sound- 
ings have  never  been  determined.  The  deep  portion  of  the 
mid-channel  is  described  as  being  narrow  when  compared  with 
its  whole  breadth  from  Cape  Horn  to  the  antarctic  continent. 

And,  when  it  is  considered,  with  the  growth  of  an  ice  age, 
how  much  of  the  ocean  waters  would  be  stored  in  the  vast 
ice-sheets  of  the  northern  hemisphere,  and  consequently  be- 
cause of  their  weight  a  large  portion  of  the  diminished  south- 


25 

ern  oceans  would  be  attracted  into  the  northern  seas,  it  seems 
that  the  bottom  of  the  shoaler  waters  of  the  Cape  Horn  chan- 
nel, which  now  comprise  so  large  a  portion  of  its  breadth, 
would  be  raised  above  the  surface  of  the  sea. 

The  one-hundred-fathom  depth  south  of  Cape  Horn,  now 
supposed  to  extend  from  longitude  70°  west  to  55°  west,  and 
southward  to  the  latitude  of  57°,  would  be  a  land  supporting 
heavy  glaciers  for  six  hundred  miles  along  the  north  side  of 
the  reduced  channel  during  the  advanced  growth  of  a  frigid 
age ;  and  the  same  conditions  would  be  obtained  in  the  vicinity 
of  the  South  Shetland.  And  when,  in  addition,  we  contemplate 
the  great  snow-fall  of  that  region,  and  the  consequent  gather- 
ing of  glaciers  which  would  occur  on  the  widened  shores  of 
the  lessened  channel,  and  the  certainty  of  their  flowing  into 
the  diminished  strait,  together  with  the  immense  icebergs  of 
such  an  age  groundingMn  the  shoaled  waters,  it  seems  that  the 
complete  obstruction  of  the  reduced  channel  would  be  accom- 
plished. 

While  contemplating  the  conditions  that  would  obtain 
while  the  Cape  Horn  channel  was  being  reduced,  it  will  be 
seen  that  the  independent  circulation  of  the  icy  southern  ocean 
would  be  carried  on  to  a  considerable  extent  even  after  the 
narrowing  strait  was  no  longer  able  to  afford  space  for  wide 
drift  currents,  for  the  reason  of  the  strong  current  that  would 
be  caused  on  account  of  the  high  ocean-level  maintained  by 
the  westerly  winds  on  the  Pacific  side  of  the  diminishing  chan- 
nel, and  the  great  low  sea-level  that  would  take  place  on  its 
Atlantic  side. 

Still,  as  previously  shown,  it  seems  that  during  an  advanced 
stage  of  the  frigid  epoch,  the  heavy  glaciers  from  the  enlarged 
northern  and  southern  shores  of  the  shrunken  channel,  to- 
gether with  the  ponderous  icebergs,  blocking  its  waters,  the 
closing  process  would  at  last  be  speedy  and  effective. 

And  on  further  consideration  it  might  be  said  that  a  channel 
of  much  less  width  and  depth  would  not  have  been  of  sum- 


26 

cient  capacity  to  have  caused  ice  periods  so  wide-spread  as 
those  that  have  left  their  traces  on  the  continents  and  islands 
of  the  globe,  for  the  reason  that  the  independent  circulation 
of  the  southern  ocean  would  not  have  been  sufficiently  com- 
plete and  long  continued  to  have  brought  such  world-wide 
cold  periods  to  perfection. 

With  the  Cape  Horn  channel  closed,  as  above  explained, 
there  would  be,  as  I  have  asserted,  a  great  change  wrought  in 
the  circulation  of  the  southern  ocean ;  for  instead  of  the  west- 
erly winds  blowing  its  surface  waters  constantly  around  the 
globe,  and  so  turning  away  and  preventing  the  entrance  of 
tropical  currents  into  the  higher  latitudes,  the  strong  prevail- 
ing westerly  winds  would  blow  the  surface  waters  of  the  sea 
from  the  Atlantic  side  of  the  closed  Cape  Horn  channel,  and 
so  cause  a  great  low  sea-level,  sufficient  to  attract  the  ocean 
waters  of  the  tropical  high  sea-level  abreast  Brazil  well  into  the 
southern  seas. 

The  winds  of  the  southern  westerly  wind-belt  being  stronger 
in  that  region  than  on  any  other  portion  of  the  globe,  conse- 
quently they  are  able  to  do  nearly  as  much  work  while  drifting 
surface  water  as  the  belt  of  westerly  wind  of  greater  width  on 
other  parts  of  the  southern  seas.  Thus  a  person  who  has  had 
a  long  experience  with  the  forcible  westerly  winds  of  the 
southern  ocean  can  well  understand  their  ability  for  disturb- 
ing the  ocean  waters  in  the  latitudes  of  the  Cape  Horn  channel. 

The  drift  currents  of  this  region  are  moved  by  the  winds 
and  waves  from  one  to  four  miles  an  hour.  Therefore,  with 
the  Cape  Horn  channel  closed,  'there  is  nothing  more  certain 
than  that  the  westerly  winds  would  be  able  to  cause  a  vast  low 
sea-level  on  the  Atlantic  side  of  the  closed  Cape  Horn  strait, 
and  that  the  waters  of  the  high  tropical  sea-level  abreast  Brazil 
would  be  attracted  to  its  wide  depression,  as  shown  on  map 
No.  1. 

The  tropical  waters  thus  attracted  far  southward  would  be 
cooler  than  the  tropical  waters  of  to-day,  owing  to  the  great 


27 

amount  of  cold  imparted  to  the  ocean  by  the  numerous  ice- 
bergs of  a  frigid  age.  Still,  they  would  begin  the  slow  process 
of  raising  the  temperature  of  the  southern  ocean,  and  would  in 
time  carry  sufficient  heat  into  the  southern  regions  to  melt  the 
ice  from  all  southern  lands  ;  for,  in  addition  to  the  Brazil  cur- 
rents, the  waters  of  the  high  sea-level  of  the  tropical  Indian 
Ocean  which  pass  southward  down  the  Mozambique  channel 
would  reach  a  much  higher  latitude  than  during  periods  when 
the  Cape  Horn  channel  was  open. 

The  ice  periods  of  the  northern  and  southern  hemispheres 
being  concurrent,  a  condition  which  I  shall  explain  in  another 
chapter,  makes  it  obvious  that  during  the  melting  of  the  gla- 
ciers from  the  antarctic  continent  and  other  southern  lands  the 
depleted  Cape  Horn  channel  could  not  gain  sufficient  capacity 
to  give  an  independent  circulation  to  the  southern  ocean  during 
the  melting  of  the  southern  ice-sheets,  on  account  of  the  dimin- 
ishing heaviness  of  the  antarctic  ice  and  the  greater  weight  of 
the  extensive  glaciers  and  augmented  seas  of  the  northern  lati- 
tudes. Consequently,  it  seems  that  the  southern  seas  would 
continue  in  a  lessened  state  while  the  glaciers  were  being  melted 
from  the  northern  hemisphere,  as  was  the  case  during  the  melt- 
ing of  the  ice  from  the  southern  hemisphere ;  and,  furthermore, 
during  such  times  the  glaciers  which  overrun  all  the  low  lands 
and  shoal  waters  of  the  Cape  Horn  region  would,  on  account  of 
their  position  being  to  the  windward  of  the  tropical  currents, 
be  the  last  great  mass  of  ice  to  melt  from  the  southern  hemi- 
sphere. 

Therefore,  it  seems  that  the  Cape  Horn  channel  would  con- 
tinue closed  or  greatly  obstructed  while  the  glaciers  were  being 
melted  from  the  lands  of  both  hemispheres.  Thus  at  length  a 
mild  climate  would  extend  over  the  globe,  and  so  remain  until 
the  prevailing  winds  slowly  forced  the  surface  waters  of  the  sea 
into  the  southern  ocean  in  the  manner  explained  in  previous 
pages,  thus  filling  the  Cape  Horn  channel  to  its  present  ca- 
pacity, and  again  restoring  the  independent  circulation  of  the 
southern  ocean. 


28 

While  contemplating  the  conditions  that  would  obtain  dur- 
ing the  melting  of  the  ice  from  the  antarctic  lands,  it  will  be 
seen  that  the  tropical  waters  attracted  to  the  great  low  sea- 
level  to  the  leeward  of  the  closed  Cape  Horn  channel  would 
eventually  enter  the  great  bight  of  the  antarctic  continent  to 
the  eastward  of  Graham  Land,  where  Captain  Weddell  sailed 
to  the  latitude  of  74°  south.  This  deep  gulf,  owing  to  its  situa- 
tion, would  receive  the  full  impact  of  the  southern  movement 
of  the  tropical  currents  ;  and,  as  the  warm  waters  spread  over 
the  wide  sea-level,  the  westerly  winds  would  convert  them  into 
a  drift  current,  and  under  such  conditions  would  be  driven 
along  the  shores  of  the  antarctic  continent,  past  the  South 
Indian  and  Pacific  Oceans,  and  eventually,  after  undergoing  a 
cooling  process  from  the  long  icy  passage,  be  forced  against  the 
Pacific  side  of  the  closed  Cape  Horn  channel  and  the  western 
Patagonian  coast. 

While  regarding  the  circulation  of  the  sea  during  an  ice 
age,  it  may  be  said  that  the  ocean's  being  composed  of  brine  was 
the  cause  of  its  waters  being  able  to  circulate  in  frigid  lati- 
tudes where  fresh  water  would  congeal.  Consequently,  this  is 
one  of  the  reasons  why  successive  periods  of  frigidity  and  mild- 
ness have  been  brought  about;  for  with  an  ocean  of  fresh 
water,  repeated  epochs  of  cold  and  warmth  could  not  have  oc- 
curred, because  a  sea  composed  of  fresh  water  would  have  con- 
gealed while  circulating  in  the  high  latitudes  during  a  frigid 
age.  Therefore,  it  required  a  sea  of  brine  to  maintain  a  liquid 
state  during  the  low  temperature  of  an  ice  period. 

For,  while  the  cold  of  a  glacial  age  increased,  the  saltness  of 
the  sea  increased  also,  because  of  the  great  amount  of  fresh 
water  evaporated  from  the  ocean,  and  stored  in  ice-sheets  on 
the  great  continents  and  islands  of  the  globe.  Thus  the  briny 
sea  was  maintained  in  a  liquid  state,  while  washing  vast  ice- 
fields and  glaciated  shores  and  floating  the  numerous  icebergs 
of  a  freezing  age.  The  cold  which  radiated  from  such  ice- 
bound seas  must  have  been  severe ;  but  meanwhile  the  evapo- 


29 

ration  from  the  ocean  was  much  reduced,  while  the  saltness 
and  coldness  of  the  sea  increased,  and  so  prevented  the  ice  of  a 
glacial  period  from  gaining  invincible  proportions  before  the 
independent  circulation  of  the  southern  ocean  was  arrested. 
Therefore,  the  remaining  warmth  of  the  tropical  waters  after 
gaining  free  access  to  the  antarctic  latitudes  was  able  to  over- 
come the  accumulated  cold  of  that  frigid  region. 

At  this  date  the  observant  navigators  who  have  visited  the 
antarctic  seas  report  that  the  surface  currents  above  the  lati- 
tude of  Cape  Horn,  while  being  drifted  eastward  by  the  prevail- 
ing westerly  winds,  also  set  toward  the  antarctic  ice  cliffs,  as 
shown  on  map  No.  2. 

The  reason  why  this  southerly  set  of  the  surface  currents  be- 
comes noticeable  above  the  latitude  of  55°  south  is  because  the 
tropical  currents  which  set  southward  from  the  torrid  latitudes 
on  the  western  sides  of  the  Atlantic,  Indian,  and  Pacific 
Oceans,  although  largely  turned  away  from  the  high  latitudes 
by  the  westerly  winds  and  drift  currents,  are  also  able  to  send 
sufficient  water  into  the  great  belt  of  westerly  winds  to  furnish 
water  for  the  deep  under-currents  setting  northward  from  the 
antarctic  shores.  Thus  the  surface  waters  moving  from  the 
north  in  order  to  gain  the  higher  latitudes,  after  entering  the 
westerly  wind-belt,  are  moved  in  drift  currents  by  the  impel- 
ling winds  easterly  over  many  degrees  of  longitude,  and  also  at 
the  same  time  slowly  southward  among  the  cooling  icebergs, 
because  of  the  attraction  caused  by  the  difference  of  tempera- 
ture and  density  between  the  northern  drift  waters  and  the  icy 
seas  of  the  antarctic  ice  barrier.  Consequently,  the  gradual 
movement  of  the  surface  waters  of  the  westerly  wind-belt 
southward  before  entering  the  higher  latitudes  is  not  generally 
apparent ;  for  it  is  after  they  enter  latitudes  where  the  globe 
becomes  much  reduced  in  circumference  that  their  southern 
movement  in  the  contracted  seas  becomes  more  noticeable. 
The  impact  of  this  southerly  current,  which  finds  its  outlet 
in  deep  under-currents,  and  retards  somewhat  the  increase  of 


30 

ice  on  the  southern  continent  at  this  date,  also  largely  prevents 
the  small  icebergs  and  field  ice  from  floating  northward,  away 
from  the  antarctic  ice  barrier ;  for  it  is  such  large  icebergs  as 
penetrate  the  deep  under-currents  that  are  the  best  able  to 
move  into  the  more  temperate  latitudes. 

From  the  above  explanations  it  will  be  seen  that  the  impact 
of  surface  water  against  the  antarctic  ice  barrier  when  the 
Cape  Horn  channel  was  closed  would  greatly  assist  the  tropical 
waters  attracted  to  the  great  low  sea-level  to  the  leeward  of 
the  obstructed  strait  to  wash  the  antarctic  shores  while  being 
drifted  eastward  by  the  westerly  winds  over  the  southern 
ocean  against  the  Patagonian  coast  and  the  Pacific  side  of  the 
closed  channel,  and  there  causing  a  high  sea-level.  This  move- 
ment of  the  winds  and  currents  encircling  the  antarctic  conti-  - 
nent  is  shown  on  map  No.  1. 

The  vast,  high  sea-level  caused  by  the  westerly  winds  drift- 
ing the  surface  waters  against  the  Patagonian  coast  would  ob- 
tain a  much  higher  plain,  were  it  not  that  so  much  of  the  water 
of  the  great  drift  current  was  required  to  feed  the  antarctic 
under-current  which  constantly  sets  northward  from  the  an- 
tarctic shores;  yet  it  would  be  sufficient  to  greatly  increase  the 
volume  of  the  Humboldt  current,  which  would  flow  in  the 
same  direction  it  now  flows,  down  the  South  American  coast  to 
the  equatorial  latitudes,  where  it  would  become  the  main 
source  of  the  great  equatorial  stream,  and  thus  offset  the  in- 
creased southward  flow  of  the  equatorial  waters  through  the 
Brazil  and  Mozambique  streams. 

The  equatorial  stream,  with  its  increased  volume,  would  also 
move,  as  it  moves  to-day,  across  the  Pacific;  and,  on  gaining 
the  western  side,  after  sending  off  large  streams  to  the  north- 
ern and  southern  latitudes,  it  would  pass  through  the  East 
India  passages  into  the  Indian  Ocean,  where  it  would  be 
drifted  westward  by  the  trade  winds  and  cause  a  high  sea-level 
abreast  the  east  coast  of  Africa,  and  so  become  the  source  of 
the  great  Mozambique  current,  which  would  flow  southward 


31 

along  the  east  coast  of  Africa,  and,  with  the  Cape  Horn  chan- 
nel closed,  would  gain  a  much  higher  latitude  than  it  would 
with  the  channel  open.  At  this  age,  when  the  continuation  of 
this  great  equatorial  stream  gains  the  latitude  of  the  Cape  of 
Good  Hope,  its  waters  are  largely  turned  eastward  by  the  great 
drift  current  of  the  southern  ocean. 

Still,  a  considerable  portion  of  its  waters  turns  toward  the 
west,  forming  the  Agulhas  current,  which  flows  around  the 
Cape  of  Good  Hope  into  the  Atlantic,  where  it  mingles  with 
the  cooler  currents  which  branch  off  from  the  great  southern 
drift  current ;  and  so,  in  connection  with  the  latter,  it  is  at- 
tracted to  the  low  sea-level  caused  by  the  south-east  trade 
winds  abreast  the  south-western  coast  of  Africa,  and  from 
thence  moved  as  a  drift  current  by  the  trade  winds  to  the  equa- 
torial Atlantic  and  coast  of  Brazil.  Thus  it  will  be  seen  that 
the  Agulhas  current,  even  with  the  Cape  Horn  channel  in  pos- 
session of  its  present  wide  capacity,  serves  to  retard  somewhat 
the  advance  of  a  cold  period. 

The  Agulhas  current  at  this  date  also  partly  serves  to  replen- 
ish the  water  which  is  forced  from  the  South  Atlantic  by 
strong  westerly  winds  into  the  Southern  Indian  and  Southern 
Pacific  Oceans.  For  it  appears  that  more  water  is  now  re- 
moved by  such  winds  from  the  South  Atlantic  than  enters  it 
from  the  South  Pacific,  even  through  the  enlarged  Cape  Horn 
channel  of  this  date ;  and  this  fact  seems  to  favor  an  impres- 
sion that  a  portion  of  this  enlarged  channel  existed  prior  to 
the  glacial  periods,  but  with  its  waters  so  much  reduced  as  to 
be  unable  to  give  the  southern  ocean  an  independent  circula- 
tion sufficient  to  exclude  the  tropical  currents  from  reaching 
the  high  southern  latitudes  in  adequate  volume  to  maintain  a 
mild  climate  in  the  southern  hemisphere. 

For  previous  to  the  glacial  age,  with  little  or  no  ice  gathered 
on  the  antarctic  lands,  it  seems  that  a  strait  possessing  one- 
half  the  capacity  of  the  Cape  Horn  channel  of  the  present  age 
could  not  prevent  the  Brazil  current  and  the  Agulhas  stream 


32 

from  flowing  into  the  southern  ocean  in  quantities  sufficient  to 
make  it  impossible  for  glaciers  to  form  on  southern  lands. 

Thus  it  is  probable  that  a  reduced  channel  separated  the 
western  continent  from  the  antarctic  lands  even  in  the  mild 
eras  previous  to  the  glacial  epochs. 

The  Cape  Horn  channel,  at  the  present  age,  with  a  capacity 
sufficient  to  largely  maintain  an  independent  circulation  for  the 
southern  ocean,  is  still  only  one-third  of  the  breadth  of  the 
westerly  wind-belt  of  the  southern  seas.  Therefore,  the  drift 
currents  do  not  all  pass  through  it  from  the  Pacific  into  the 
Atlantic.  Consequently,  a  considerable  portion  of  the  drifted 
water  turns  northward  west  of  Cape  Horn,  and  so  forms  the 
Humboldt  current. 

The  Agulhas  stream,  which  even  now  assists  in  replenishing 
the  South  Atlantic  with  tropical  water,  would,  during  the  per- 
fection of  a  glacial  period,  with  the  Cape  channel  closed,  be 
a  much  stronger  stream  than  it  now  obtains  with  the  Cape 
channel  possessing  its  present  enlarged  capacity,  for  the  rea- 
son that  the  South  Atlantic  waters  would  continue  as  now  to 
be  forced  eastward  by  the  westerly  winds,  while  they  could  not 
be  replenished,  as  they  are  to-day,  directly  from  the  South 
Pacific. 

Consequently,  the  waters  of  the  South  Atlantic  Ocean  would 
be  correspondingly  reduced. 

Such  conditions  alone  would  greatly  increase  the  volume  of 
the  Agulhas  stream  at  the  culmination  of  a  frigid  age.  There- 
fore, the  work  of  subduing  a  frigid  period  in  the  southern  hem- 
isphere after  the  Cape  Horn  channel  was  closed  would  not  rest 
on  the  Brazil  current  alone,  but  also  on  the  great  equatorial 
stream  of  the  Pacific  and  Indian  Oceans. 

Yet  during  such  frigid  times  the  sources  of  the  equatorial 
stream  would  be  greatly  chilled  by  its  two  great  feeders,  the 
Humboldt  current  and  the  returning  Japanese  current,  both 
of  which  flow  down  from  the  high  latitudes  and  meet  in  the 
equatorial  latitudes  on  the  eastern  side  of  the  Pacific,  thus 
cooling  the  source  of  the  great  equatorial  current. 


33 

But  this  latter  stream,  while  on  its  long  western  passage 
across  the  Pacific  and  Indian  Oceans,  beneath  a  torrid  sun, 
with  only  one  cold  feeder  from  the  south  which  approaches  it 
along  the  west  side  of  Australia,  would,  on  its  long  tropical 
journey,  be  able  to  obtain  considerable  warmth,  even  during  an 
ice  period,  to  supply  the  Mozambique  and  Agulhas  streams, 
and  so  greatly  assist  the  Atlantic  waters  in  bringing  about  a 
mild  period.  Still,  the  process  of  subduing  the  cold  of  the 
southern  latitudes  would  be  slow,  even  with  the  Cape  Horn 
channel  closed,  because  of  the  vast  collection  of  ice  burdening 
the  sea  and  land. 

Yet  there  were  conditions  that  were  naturally  brought  about 
to  favor  the  process  of  returning  warmth  ;  for  it  appears  that, 
when  the  southern  ocean  was  made  shallow  because  of  a  con- 
siderable portion  of  its  waters  having  been  moved  into  the 
northern  hemisphere,  it  will  be  seen  that  the  conditions  were 
more  favorable  for  the  westerly  winds  to  create  drift  currents 
than  would  be  the  case  on  deeper  seas.  Therefore,  the  high  and 
low  sea-levels  caused  by  such  winds  would  be  greater  on  a  shal- 
low ocean  than  would  occur  on  deeper  waters.  Thus  the  low 
sea-levels  of  the  shallow  southern  sea  would  have  strong  attrac- 
tion for  tropical  surface  waters,  and  so  increase  the  thickness  of 
its  warm  drift  currents,  and  at  the  same  time  its  lessened  depths 
would  have  less  capacity  for  the  storage  of  cold  water  to  re- 
duce the  temperature  of  the  under-waters  of  the  tropical  zone. 

And,  furthermore,  when  the  southern  ocean  was  shallow, 
New  Zealand  acquired  a  longer  extension  of  land  to  the  north 
and  south.  Consequently,  the  enlarged  low  sea-level  on  its 
eastern  side  attracted  more  tropical  water  into  the  southern  lat- 
itudes than  now. 

So,  according  to  the  conditions  I  have  pointed  out,  the  ice- 
sheets  would  at  length  melt  away,  and  a  long  period  of  mild- 
ness would  succeed  on  account  of  the  length  of  time  it  would 
require  after  the  ice  disappeared  from  the  earth  for  the  pre- 
vailing winds  to  move  the  surface  waters  of  the  augmented 


34 

northern  seas  into  the  southern  ocean,  and  again  restore  its 
independent  circulation,  and  so,  after  a  considerable  lapse  of 
time,  bring  about  the  geographical  and  climatic  conditions  ex- 
isting at  the  present  date,  which  can  be  seen  on  map  No.  2, 
which  shows  that  a  cold  period  has  already  made  considerable 
advance  in  the  southern  hemisphere,  the  southern  continent 
and  islands  being  covered  with  glaciers,  and  the  prevalence  of 
icebergs  as  far  north  as  the  latitude  of  35°  south. 

Moreover,  when  we  consider  that  the  independent  circula- 
tion of  the  southern  ocean  is  caused  by  the  westerly  winds 
blowing  its  surface  waters  constantly  around  the  globe  through 
the  open  Cape  Horn  channel,  and  so  largely  preventing  the 
tropical  currents  from  entering  the  high  southern  latitudes, 
and  how,  in  consequence,  the  cold  is  slowly  on  the  increase 
through  the  constant  accumulation  of  ice  on  the  lands  and  in 
seas  of  the  southern  latitudes,  it  appears  that  a  frigid  age  is 
slowly  progressing  in  the  southern  hemisphere.  For  it  seems 
that  continental  ice-sheets  should  not  only  be  able  to  retain 
their  freezing  temperature,  but  also  the  mean  of  the  low  tem- 
perature in  which  they  were  formed,  for  a  considerable  length 
of  time,  and  so  impart  their  extreme  coldness  in  the  shape  of 
icebergs  into  such  seas  as  border  on  the  glaciated  lands. 

It  has  been  proved  at  Point  Barrow  that  strata  of  ice  and 
gravel  can  maintain  a  wintry  temperature  through  the  sum- 
mer months.  Captain  G.  B.  Borden,  keeper  of  the  refuge  sta- 
tion in  that  region,  states  that  Lieutenant  Ray,  of  the  Signal 
Service,  excavated  through  ice  and  gravel  to  a  depth  of  forty- 
one  feet,  and  that  the  lower  portion  of  the  excavation  main- 
tains a  temperature  15°  Fahrenheit  above  zero  the  year  around. 
Therefore,  with  the  probability  of  southern  glaciers  obtaining 
a  temperature  of  over  15°  Fahrenheit  below  the  freezing  point, 
we  can  well  realize  the  frigidity  imparted  to  the  southern 
oceans  while  melting  numerous  immense  icebergs,  and  con- 
sequently will  conclude  that  the  temperature  of  the  southern 
latitudes  is  gradually  lowering. 


35 

The  icebergs  of  the  antarctic  seas  would  not  move  northward 
into  the  temperature  latitudes  so  readily  as  they  now  do,  were 
it  not  that  the  general  southward  set  of  the  southern  ocean 
currents  were  interrupted  by  the  movement  of  northerly  sur- 
face currents  in  the  longitudes  of  the  low  sea-levels,  caused  by 
the  westerly  winds  drifting  the  surface  waters  of  the  sea  from 
the  eastern  coasts  of  Southern  South  America  and  New  Zea- 
land. For  it  is  owing  to  the  low  sea-levels  thus  created,  in 
connection  with  the  deep  under-currents  which  set  northward 
from  the  ice  cliffs  of  the  antarctic  lands,  that  many  icebergs 
are  enabled  to  move  into  the  temperate  latitudes,  especially  to 
seas  north-east  of  the  Falkland  Islands. 

On  other  portions  of  the  southern  ocean  above  the  latitude  of 
55°  south  the  surface  waters,  while  being  drifted  eastward  by 
the  strong  westerly  winds,  also  set  toward  the  antarctic  shores, 
and  so  furnish  water  for  the  cold  under-currents  which  set 
northward  from  that  frigid  region.  Thus  from  such  parts  of 
the  coast  only  the  largest  bergs,  which  require  a  deep  sea  to 
float  them,  are  moved  by  the  under-currents  into  the  temperate 
latitudes.  Therefore,  it  happens  that,  while  an  ice  period  pro- 
gresses, and  the  antarctic  icebergs  increase  in  size,  the  more 
readily  the  cold,  deep  under-currents  force  them  into  the  tem- 
perate zone,  in  opposition  to  the  winds  and  surface  currents. 

The  icebergs,  after  gaining  the  temperate  latitudes,  are 
moved  more  or  less  eastward  by  the  westerly  winds  and  drift 
currents,  and  so  are  scattered  over  the  southern  temperate 
oceans,  where  the  melting  bergs  impart  whatever  coldness  they 
were  able  to  store  up  while  forming  in  the  antarctic  regions. 

The  low  sea-levels  caused  by  the  westerly  winds  to  the  lee- 
ward of  New  Zealand  and  to  the  leeward  of  Argentine,  not  only 
cause  the  ice-bearing  currents  to  set  northward,  but  they  also 
cause  the  tropical  currents  to  make  considerable  inroads  into 
the  high  southern  latitudes.  This  is  the  reason  why  the  lands 
are  less  burdened  with  ice  on  the  antarctic  shores  opposite  Cape 
Horn  than  on  other  parts  of  that  glaciated  continent. 


36 

The  tropical  currents  which  turn  southward  east  of  New  Zea- 
land largely  mingle  their  waters  with  the  great  southern 
drift  current,  and  so  are  carried  through  the  Cape  Horn  chan- 
nel. Owing  to  this  cause,  the  antarctic  lands  abreast  Cape 
Horn  are  less  burdened  with  ice  than  other  portions  of  the 
antarctic  shores. 

Thus,  were  it  not  for  this  penetration  of  warm  waters  south- 
ward, the  antarctic  coasts  south  of  Cape  Horn,  because  of  the 
great  snow-fall  of  that  region,  would  obtain  heavier  glaciers 
than  other  portions  of  the  southern  continent.  But  the  time  is 
slowly  coming  when,  with  a  lower  temperature,  the  ice-sheets 
on  the  lands  in  the  vicinity  of  the  South  Shetlands  will  attain 
greater  thickness  than  the  glaciers  on  other  shores  of  the 
antarctic  continent. 

Hence  it  appears  that,  when  the  several  agents  for  producing 
and  distributing  cold  in  the  southern  latitudes  are  taken  into 
consideration,  the  immense  and  continuous  storage  of  ice  on 
the  southern  lands,  which  adds  to  the  wide-spread  fleet  of  ice- 
bergs that  float  the  southern  temperate  seas,  and  also  the  vast 
movement  of  cold  antarctic  water  into  the  temperate  and  trop- 
ical oceans  in  deep  under-currents,  combined  with  the  increas- 
ing coldness  of  the  westerly  winds,  are  now  slowly  bringing 
about  in  the  southern  hemisphere  a  period  of  frigidity. 


37 


CHAPTER  II. 

HOW   ICE   PERIODS   IK   THE   NORTHERN   HEMISPHERE    ARE 
BROUGHT   ABOUT. 

A  LARGE  number  of  geologists  are  of  the  opinion  that 
during  the  whole  of  the  Tertiary  period  the  climate  of  the 
northern  temperate  and  arctic  latitudes  was  uniformly  warm, 
without  a  trace  of  intervening  frigid  periods.  I  have  before 
explained  why  the  climate  was  made  warm  in  the  southern 
hemisphere  during  the  Tertiary  epoch,  and  how  on  the  closing 
of  that  age,  and  subsequently,  a  considerable  portion  of  the 
ocean  waters  had  moved  from  the  northern  hemisphere  into  the 
southern. 

Therefore,  the  northern  seas  during  Tertiary  times  covered 
a  much  larger  area  than  have  obtained  during  periods  following 
that  mild  epoch.  So,  when  the  low  lands  of  Europe  were  sub- 
merged, the  Baltic,  .Caspian,  and  other  neighboring  seas,  now 
land-locked,  were  a  portion  of  an  enlarged  Atlantic.  Conse- 
quently, the  westerly  winds  blew  over  a  much  wider  North 
Atlantic  than  during  the  later  periods. 

Thus  the  high  sea-level  caused  by  such  winds  on  its  European 
side  was  greater  than  has  since  been  obtained  with  the  Atlan- 
tic of  less  breadth.  This  high  sea-level,  composed  largely  of 
drift  water  from  the  ancient  Gulf  Stream,  had  convenient 
access  to  the  enlarged  Arctic  Ocean,  which  then  covered  the 
low  plains  of  Northern  Europe  and  Siberia.  And  owing  to  the 
trend  of  elevated  lands  north-eastward,  which  then  formed  the 
southern  shores  of  the  Arctic  Ocean  in  those  regions,  the  warm 
waters  of  the  high  sea-level  of  the  Eastern  North  Atlantic 
found  an  easy  passage  into  the  arctic  seas ;  for,  while  they 
moved  over  the  European  and  Siberian  seas  to  the  north-east, 
they  had  the  assistance  of  the  westerly  winds  well  into  the 
arctic  seas,  from  which  position  they  were  attracted  across  the 


394727 


38 

Arctic  Ocean  to  the  low  sea-level  abreast  Labrador  and  Davis 
Strait. 

The  Gulf  Stream  of  Tertiary  times  comprised  a  much  larger 
area  than  it  now  obtains ;  for  with  Florida  and  a  large  portion 
of  the  Gulf  States  submerged,  and  a  wide,  shallow  sea  covering 
the  Mississippi  valley  and  the  Great  Lake  region,  the  tropical 
waters  of  the  enlarged  Gulf  of  Mexico  moved  from  their  vast 
high  sea-level  to  the  low  sea-level  abreast  British  America  and 
Labrador,  without  being  confined  to  the  narrow  Florida  chan- 
nel. Thus  with  an  enlarged  Gulf  Stream  in  possession  of  a 
wide  and  clear  passage  leading  northward,  in  connection  with 
a  mild  period  in  the  southern  hemisphere,  giving  warmth  to 
the  southern  oceans,  the  resources  of  the  ancient  Gulf  currents 
for  warming  the  northern  regions  were  so  ample  and  inex- 
haustive  they  were  fully  able  to  maintain  a  mild  climate  on 
the  shores  of  the  European  seas,  and  also  on  the  shores  border- 
ing the  Arctic  Ocean,  during  the  Tertiary  epoch. 

Furthermore,  the  Humboldt  current,  which  had  its  rise  in 
the  mild  southern  seas  of  that  age,  mingled  its  warmth  with 
the  equatorial  current  of  the  Pacific,  which  in  turn  gave  its 
warmth  to  the  Japanese  current.  Therefore,  the  latter  stream 
under  such  conditions  was  competent  to  maintain  a  mild 
climate  on  the  North  Pacific  coasts. 

The  origin  of  a  cold  period  in  the  northern  hemisphere  was 
largely  owing  to  the  changed  condition  of  the  northern  oceans 
following  the  close  of  the  Tertiary  epoch.  The  movement  of 
the  ocean  waters  into  the  southern  hemisphere  lessened  the 
area  of  the  Arctic  and  North  Atlantic  Oceans,  and  brought 
them  to  their  present  reduced  limits,  and  also  diminished  the 
volume  of  the  Gulf  currents. 

This  great  geographical  change,  in  connection  with  a  cold 
period  progressing  in  the  southern  hemisphere,  and  so  increas- 
ing the  coldness  of  the  Japanese  current,  and  the  cold  antarctic 
currents,  previously  explained,  which  set  northward  on  the 
bottom  of  the  sea  through  the  torrid  latitudes  even  into  the 


39 

North  Pacific  and  North  Atlantic  Oceans,  were  altogether 
sufficient  to  cause  conditions  favorable  for  the  advancement 
of  a  cold  period  in  northern  latitudes.  Besides,  with  reduced 
northern  oceans  and  a  diminished  Gulf  current,  conditions  were 
favorable  for  an  independent  circulation  of  the  arctic  waters, 
such  as  is  being  carried  out  at  the  present  time.  Hence  an  ex- 
planation of  the  movements  of  the  ocean  waters  of  to-day  will 
explain  the  conditions  which  caused  the  northern  ice  periods  in 
times  past,  as  well  as  those  to  come  in  a  future  age.  Although 
the  conditions  are  such  that  the  independent  circulation  of 
the  arctic  waters  cannot  be  so  well  performed  as  the  indepen- 
dent circulation  of  the  southern  ocean,  still  the  open  arctic 
channels  are  able  to  prevent  the  tropical  Gulf  Stream  water 
from  largely  entering  the  higher  northern  latitudes.  For  it  is 
certain  that  the  prevailing  westerly  winds  blow  the  surface 
waters  of  the  North  Atlantic  away  from  the  eastern  shores  of 
North  America  from  Georgia  to  Labrador. 

Consequently,  the  low  sea-level  thus  caused  attracts  the 
waters  of  the  Arctic  Ocean  southward  through  Baffin's  Bay 
and  Davis  Strait,  and  likewise  down  the  east  coast  of  Green- 
land, thus  surrounding  that  large  island  with  an  arctic  tem- 
perature, and  so  causing  it  to  become  a  land  of  glaciers,  which 
are  constantly  launching  icebergs  into  the  sea  to  cool  the  waters 
of  the  northern  oceans.  The  tropical  waters  of  the  high  sea- 
level  of  the  Gulf  of  Mexico  also  seek  the  low  sea-level  abreast 
the  American  coast,  thus  causing  the  Gulf  Stream.  This  great 
ocean  current,  being  the  main  conveyer  of  tropical  heat  into  the 
high  latitudes  of  the  North  Atlantic,  calls  for  particular  notice. 
The  great  gravity  currents,  of  which  the  Gulf  Stream  is  one  of 
the  most  conspicuous,  are  moved  by  small  gradients. 

Hence  the  gradient  which  causes  the  Gulf  Stream  waters  to 
move  out  of  the  Florida  passage  is  small.  The  levellings 
which  have  been  made  place  the  surface  waters  of  the  Gulf 
of  Mexico  as  being  about  one  metre  higher  than  the  Atlantic 
abreast  New  York,  the  pressure  of  the  higher  Gulf  waters 


40 

toward  the  low  level  of  the  Atlantic  being  nearly  equal  in 
the  narrow  Florida  channel  from  the  surface  to  the  bottom 
of  the  stream.  Therefore,  according  to  descriptions  given  by 
Commander  Bartlett,  the  warm  stream  moves  like  a  river  over 
the  hard  level  floor  of  the  channel;  but  to  the  northward  of 
the  Bahamas,  abreast  Cape  Hatteras,  the  stream  spreads  out  in 
fanlike  form,  and  flows  over  a  bed  of  cold  water  of  great  depth. 

A  bed  of  cold  water  is  found  to  cover  the  bottom  of  all  the 
deep  oceans  that  are  accessible  to  the  antarctic  seas,  through 
which  the  cold  water  is  mostly  supplied,  as  I  have  before 
pointed  out. 

But  the  cold  water  which  underruns  the  Gulf  Stream  is 
probably  furnished  by  the  arctic  waters  which  move  down 
Davis  Strait  and  the  east  coast  of  Greenland.  The  Gulf 
Stream,  as  it  widens  and  becomes  more  shallow,  is,  through 
its  exposure  to  the  westerly  winds,  gradually  converted  into  a 
drift  current;  and  in  this  way  its  surface  waters  are  forced 
over  abreast  the  shores  of  Western  Europe,  where  it  imparts  its 
warmth  to  a  wide  region,  and  also  causes  a  high  sea-level. 
A  portion  of  the  waters  of  this  high  sea-level  turn  southward 
to  replenish  the  waters  which  have  been  moved  by  the  trade 
winds  from  the  eastern  tropical  North  Atlantic  over  into  the 
Caribbean  Sea  and  Gulf  of  Mexico,  while  its  northern  and 
smaller  portion  mingles  with  the  Arctic  Ocean  waters  north 
of  Europe.  These  latter  waters,  having  escaped  from  the 
westerly  wind-belt,  and  acquired  a  high  sea-level,  and  also 
made  cool  on  mingling  with  the  icy  arctic  seas,  lose  a  part  of 
their  bulk  on  becoming  chilled  by  sinking  and  returning  in 
under-currents  to  the  seas  from  which  they  were  forced  by 
the  south-westerly  winds ;  while  the  larger  remaining  surface 
waters  set  across  the  Arctic  Ocean  over  to  the  northern  coast 
of  Greenland,  and  so  down  the  east  and  west  coasts  of  that 
large  island  to  the  low  sea-level  abreast  the  American  coast, 
where  the  cold  waters  not  only  crowd  the  Gulf  Stream  from  the 
shore,  but  they  also  sink  under  it,  and  form  the  vast  bed  of 


41 

cold  water  over  which  the  Gulf  currents  flow.  This  cold 
underflow  of  water  southward  probably  joins  the  deep  antarc- 
tic currents  south  and  south-east  of  the  Bermuda  Islands,  and 
returns  to  the  tropical  latitudes  a  portion  of  the  water  that  is 
carried  into  the  Arctic  Ocean  by  the  Gulf  Stream. 

There  are  times  during  the  late  summer  and  early  fall  months 
when  the  arctic  channels  are  considerably  obstructed  by  ice- 
bergs, and  the  low  sea-level  of  Davis  Strait  and  Baffin's  Bay, 
with  the  assistance  of  occasional  south-east  winds,  is  able  to 
attract  the  temperate  waters  of  the  Atlantic  as  far  north  as  the 
Arctic  Circle.  Also  from  the  same  cause  the  icy  waters  which 
flow  down  the  east  coast  of  Greenland  are  attracted  along  its 
southern  and  south-western  shores  into  Davis  Strait. 

Yet  at  the  same  time  the  icy  waters  which  flow  from  Smith's 
Sound  and  other  arctic  channels  move  in  a  counter-current 
down  the  westerly  side  of  Baffin's  Bay  and  Davis  Strait,  and  so 
carry  the  icebergs  and  field-ice  past  Labrador  and  Newfound- 
land well  on  to  the  borders  of  the  Gulf  Stream.  And,  according 
to  Lieutenant  Maury,  the  westerly  gales  of  the  winter  months 
force  the  temperate  waters  of  the  Atlantic,  which  pertain  to 
the  Gulf  Stream,  several  degrees  away  from  the  south-east 
coast  of  Greenland.  Therefore,  during  such  seasons  the  surface 
waters  of  the  returned  arctic  currents,  which  flow  down  the 
east  coast  of  Greenland  and  Davis  Strait,  are  drifted  past 
Southern  Greenland  and  Iceland,  and  so  onward  into  the  arctic 
seas,  north  of  Europe.  Thus  the  arctic  waters  maintain  an 
independent  circulation  sufficient  to  largely  exclude  the  Gulf 
Stream  from  the  arctic  seas,  and  surround  Greenland  with  an 
arctic  temperature;  and  it  is  on  this  account  glaciers  have 
formed  on  Greenland  and  other  arctic  shores,  and  such  glaciers 
are  probably  increasing,  as  every  iceberg  launched  from  the 
frigid  lands  and  floated  to  the  lower  latitudes  lowers  somewhat 
the  temperature  of  the  North  Atlantic,  and  so  causes  conditions 
favorable  for  larger  accumulations  of  ice  on  the  arctic  shores. 

Yet  it  is  probable  that  an  ice  period  extending  over  the 


42 

northern  temperate  zone  could  not  be  perfected  by  this  process 
alone,  should  the  tropical  and  southern  oceans  maintain  their 
present  temperature.  But,  with  the  assistance  of  a  frigid 
period  in  the  southern  hemisphere  to  cool  the  ocean  waters,  and 
thus  lower  the  temperature  of  all  tropical  currents,  including 
the  Gulf  Stream  and  Japan  currents,  an  ice  age  could  be 
brought  about  in  the  northern  hemisphere  equal  in  intensity 
to  the  glacial  periods  of  the  past. 

And,  when  we  know  that  a  considerable  portion  of  the  heat 
carried  into  the  northern  latitudes  by  tropical  streams  is  largely 
derived  through  the  mingling  of  the  waters  of  such  currents 
with  the  warm  waters  of  the  southern  tropical  oceans,  it  is 
evident  that  the  ice  periods  of  the  northern  and  southern  hemi- 
spheres were  concurrent;  although  the  culmination  of  the 
northern  frigid  period  would  be  somewhat  later  than  the  per- 
fected southern  ice  age,  on  account  of  the  northern  seas  requir- 
ing the  assistance  of  the  cold  oceans  of  the  southern  hemisphere 
to  perfect  a  northern  ice  age. 

The  small  area  of  the  northern  seas,  compared  with  the 
southern  oceans,  and  the  wide  mingling  of  the  ocean  waters  of 
the  hemispheres,  make  it  evident  that  the  comparatively  scanty 
northern  seas  could  not  bring  about  or  maintain  either  a  frigid 
or  mild  period  in  opposition  to  the  superior  oceans  of  the 
southern  hemisphere. 

On  the  consummation  of  an  ice  period  in  the  northern  hemi- 
sphere heavy  glaciers  covered  the  larger  portion  of  its  conti- 
nents and  islands,  which  added  so  much  weight  to  the  northern 
lands  as  to  attract  the  waters  of  the  southern  oceans  into  the 
northern  latitudes,  as  I  have  before  explained. 

Thus,  when  the  ice  was  mostly  melted  from  the  lands  of  the 
southern  hemisphere,  the  heavy  ice-sheets  that  remained  on 
the  extensive  northern  lands  would  still  continue  to  attract 
the  warm  waters  of  the  southern  seas  into  the  northern  oceans ; 
and  in  this  way  the  Japanese  and  Gulf  currents  would  gain  a 
higher  temperature  and  greater  volume,  and  thus  add  to  their 


43 

ability  for  melting  the  northern  glaciers  wherever  they  were 
able  to  flow,  and  so  hasten  the  growth  of  a  mild  era  in  the 
northern  hemisphere. 

And  it  seems  reasonable  to  suppose  that  there  was  more 
water  in  the  northern  hemisphere  on  the  ending  of  its  ice 
period  than  at  this  age ;  yet  it  appears  that  it  was  returned  to 
the  southern  hemisphere  during  a  short  period  by  the  prevailing 
winds  in  the  manner  which  I  have  previously  explained. 

Therefore,  there  are  but  few  traces  of  such  flowage  to  be 
found  in  the  glacial  drift,  especially  with  the  scarcity  of  marine 
life  after  the  rigor  of  a  frigid  age. 

An  article  in  Science,  July  5,  1895,  written  by  Agnes  Crane, 
states  that  Professor  Joseph  Prestwich  has  recently  contrib- 
uted a  suggestive  memoir  on  this  subject  to  the  Philosophical 
Transactions  of  the  Royal  Society.  It  treats  of  the  evidence 
of  a  submergence  of  Western  Europe  and  the  Mediterranean 
coasts  at  the  close  of  the  glacial  period ;  and  in  a  previous 
paper  communicated  to  the  Geological  Society  of  London,  in 
1892,  the  author  gave  evidence,  deduced  from  personal  obser- 
vation, of  the  submergence  of  the  south  of  England  not  less 
than  a  thousand  feet,  at  the  close  of  the  glacial  epoch. 

Since  that  time  the  flood  of  water  which  flowed  all  of  the 
low  lands  of  the  high  northern  latitudes  has  been  returned  to 
the  southern  seas,  because  of  the  force  of  the  prevailing  winds 
in  connection  with  the  great  oceans  which  open  so  widely 
toward  the  south,  the  force  of  the  winds  being  assisted  through 
the  attraction  caused  by  the  difference  of  temperature  in  the 
surface  waters  of  the  vast  southern  temperate  oceans  and  the 
antarctic  seas,  and  in  this  manner  bringing  about  the  geograph- 
ical conditions  of  to-day  which  favor  the  return  of  another 
ice  age. 

It  is  said  by  those  who  attribute  the  great  currents  of  the 
ocean  to  the  rotation  of  the  earth  that  the  winds  have  little  to 
do  in  causing  such  currents  as  the  Gulf  Stream.  But  my  im- 
pression is  that  the  southern  portion  of  the  Gulf  Stream 


44 

waters,  after  being  drifted  by  westerly  winds  over  abreast 
Europe,  are  attracted  to  the  low  sea-level  in  the  vicinity  of  the 
Canary  Islands,  to  be  moved  by  the  trade  winds  toward  the 
equatorial  calm  belt  and  the  West  India  Islands.  And  dur- 
ing my  many  months'  cruising  over  these  seas  I  have  had  my 
attention  directed  to  the  singular  action  of  the  surface  waters, 
while  being  impelled  by  the  trade  winds  toward  the  West  India 
sea ;  for  during  the  first  fifteen  hundred  miles  of  their  passage 
they  are  moved  by  the  prevailing  easterly  winds  without  much 
apparent  resistance  or  unusual  disturbance.  But  on  nearing 
the  longitude  of  Cape  St.  Roque,  and  having  acquired  a  high 
sea-level  from  which  there  is  no  easy  or  wide  outlet,  the  im- 
pelled surface  waters  begin  to  rebel  against  the  forceful  winds, 
and  cause  a  remarkable  commotion  in  the  shape  of  tide-rips 
and  white-capped  ripples,  which  extend  from  the  equator  in  a 
northerly  direction  to  the  latitude  of  about  19°  north,  thus 
crossing  the  central  portion  of  the  north-east  trade-wind  belt, 
with  a  breadth  of  over  three  hundred  miles,  as  shown  on  map 
No.  2. 

This  disturbed  region  where  the  winds  and  waters  conflict 
is  the  probable  fountain-head  of  the  Gulf  Stream.  The  reason 
why  the  surface  waters  of  this  disturbed  portion  of  the  Atlan- 
tic do  not  flow  peacefully  along  through  the  West  India  pas- 
sages into  the  Caribbean  Sea  and  Gulf  of  Mexico  is  because  of 
their  narrow  outlet  at  the  Florida  channel.  For  it  is  mainly 
through  this  narrow  channel  that  the  vast  waters  of  the  tropi- 
cal high  sea-level  are  attracted  to  the  low  ocean-level  of  the 
Western  North  Atlantic. 

Thus  it  seems  that  the  great  fountain-head  of  the  Gulf 
Stream  is  situated  between  the  wide  tide-rips  and  the  Carib- 
bean Islands.  The  waters  from  this  high  ocean-level  enter  the 
Caribbean  Sea  mainly  through  the  several  passages  south  of 
Guadeloupe ;  while  the  northern  portion  of  the  raised  waters 
set  mostly  toward  the  north-west,  and  so  unite  with  the  east- 
ern portion  of  the  Gulf  currents  after  they  enter  the  Atlantic. 


45 

Still,  the  great  high  sea-level  which  presses  against  the  Wind- 
ward Islands,  being  somewhat  higher  than  the  Caribbean  Sea, 
forces  its  waters  through  the  island  passages  in  quantities  suf- 
ficient to  supply  the  Gulf  Stream ;  and  there  are  times  when 
the  winds  are  so  strong  and  favorable  that  all  of  the  passages 
east  of  Cuba  conduct  water  into  the  Caribbean  Sea,  the  cold 
under-waters  entering  the  deeper  channels  as  well  as  the  warm 
surface  waters.  Yet  the  currents  setting  through  these  numer- 
ous channels  are  subject  to  fluctuations,  and  so  also  is  the  Gulf 
Stream  which  they  supply. 

That  portion  of  the  high  sea-level  south  of  Guadeloupe  re- 
ceives considerable  assistance  as  a  feeder  for  the  Gulf  Stream 
through  being  connected  on  the  south  by  the  great  high  sea- 
level  abreast  Brazil  and  the  great  high  sea-level  of  the  equato- 
rial calm  belt.  The  latter  high  level  is  caused  by  the  trade 
winds,  which  generally  blow  briskly  down  the  coast  of  Sahara, 
and  also  further  off  shore,  and  ending  south  of  the  Cape  Verde 
Islands  somewhat  abruptly  in  the  equatorial  calm  belt. 

The  south-east  trades  which  blow  over  the  Eastern  and  Mid- 
dle South  Atlantic  terminate  on  the  southern  side  of  the  calm 
region.  Therefore,  the  two  trade  winds  impel  the  surface 
waters  of  the  tropical  Atlantic  from  opposite  directions  di- 
rectly toward  the  calm  belt,  and  so  raise  its  waters  above  the 
common  level  of  the  sea. 

This  is  the  opinion  of  the  writers  of  the  South  Atlantic 
Directory.  Still,  it  is  probable  that  the  high  ocean-level  of  the 
calm  belt  is  but  slightly  raised  above  the  common  level  of  the 
sea,  ou  account  of  the  trade  winds  having  to  contend  against 
the  tendency  of  the  warm  tropical  surface  waters  to  move 
toward  the  polar  latitudes.  The  calm  belt  expanse  which  ex- 
tends from  Africa,  where  it  attains  its  greatest  width,  gradually 
narrows  as  it  extends  westward  to  the  longitude  of  Cape  St. 
Roque,  where  it  attains  its  highest  sea-level,  on  account  of  the 
borders  of  its  narrowing  space  being  impelled  westward  by  the 
trade  winds. 


46 

The  movement  of  the  waters  of  this  high  ocean-level  is 
mostly  toward  the  west,  forming  a  portion  of  the  equatorial 
current  of  the  Atlantic.  The  reason  of  its  western  movement 
is  on  account  of  its  raised  waters  being  able  to  supply  a  portion 
of  the  Gulf  Stream  with  water  which  is  sent  off  in  a  westerly 
current  along  the  South  American  coast,  west  of  Cape  St. 
Roque  into  the  Caribbean  Sea;  while,  on  the  other  hand,  it 
joins  with  the  great  high  sea-level  abreast  Brazil,  and  so  unites 
with  its  great  southern  current.  The  gradient  of  the  high  sea- 
level  of  the  calm  belt  on  its  southern  side  probably  extends 
south  of  the  equator,  on  account  of  the  south-east  trades  being 
weak  in  latitudes  near  the  equator ;  while  on  the  north  side 
the  north-east  trades  generally  blow  brisk  and  end  more 
abruptly,  so  producing  a  gradient  of  less  width  than  that  of  the 
South  Atlantic  side. 

It  does  not  appear  that  the  seas  of  the  high  northern  lati- 
tudes gain  an  undue  proportion  of  the  tropical  Atlantic  waters, 
because  of  the  south-east  trades  extending  north  of  the  equator, 
on  account  of  such  winds  being  weak,  and  the  waters  of  the 
high  sea-level  of  the  Western  North  Atlantic  having  narrow 
and  otherwise  obstructed  passages  leading  to  its  northern  seas. 
Yet  the  high  sea-level  of  the  equatorial  calm  belt  is  always 
ready,  whenever  a  favorable  grade  is  formed  by  a  monsoon  or 
otherwise,  to  run  off  its  surplus  water  obtained  by  winds  and 
rain ;  and  I  have  noticed,  while  cruising  in  these  seas,  that  it 
happens  at  times  during  the  northern  winter  months  when  the 
north-westerly  gales  drive  the  surface  waters  of  the  North- 
western Atlantic  toward  the  tropical  zone,  and  at  the  same 
time  a  strong  north-east  monsoon  is  prevailing  along  the  south- 
ern coast  of  Brazil,  the  westerly  currents  setting  past  the  Ama- 
zon River  are  reversed,  and  set  to  the  south-east,  while  such 
conditions  last. 

For,  when  the  summer  solstice  is  in  the  south,  and  the  north- 
east monsoon  moves  southward  along  the  coast  of  Brazil,  much 
equatorial  water  moves  off  in  that  direction ;  and  during  the 


47 

same  season  the  cooled  Sahara  has  an  outward  flow  of  air 
toward  the  south,  which  moves  more  or  less  water  from  the 
coast  of  Guinea,  which  is  easily  accomplished,  because  the 
warm  surface  waters  of  that  coast  are  inclined  to  join  with  the 
south  equatorial  stream.  Consequently,  the  waters  move  from 
their  high  sea-level  north  of  Cape  Palmas,  and  so  form  the 
Guinea  current. 

The  high  sea-level  of  the  equatorial  calm  belt  of  the  Atlantic 
contains  a  large  portion  of  the  conserved  heat  of  the  tropical 
Atlantic,  which  at  this  age  sends  off  a  somewhat  limited  supply 
of  warm  water  to  the  Gulf  Stream,  and  also  to  the  Brazil  cur- 
rent. But,  whenever  the  Cape  Horn  channel  is  closed  or  much 
obstructed,  so  causing  a  great  low  sea-level  in  the  Southern  At- 
lantic, the  tropical  waters  heaped  against  Brazil,  and  the  raised 
waters  of  the  great  calm  region  being  one  continuous  high  sea- 
level,  would  mostly  be  attracted  to  the  vast  low  sea-level  of  the 
southern  ocean.  Hence  it  will  be  seen  how  large  a  portion  of 
the  conserved  heat  of  the  tropical  Atlantic  would  be  used  to 
warm  the  high  southern  latitudes  during  a  warm  period  in  the 
southern  hemisphere,  and  at  the  same  time  the  head-waters  of 
the  Gulf  Stream  would  obtain  the  same  height  as  now.  For 
we  now  see  much  of  the  force  of  the  north-east  trade  winds  lost, 
while  maintaining  so  large  a  high  sea-level  to  the  windward  of 
the  West  India  Islands,  which  is  probably  capable  of  supplying 
a  stream  of  double  the  capacity  of  the  gulf  current  which 
passes  through  the  Florida  channel. 

And  it  appears,  while  viewing  the  vast  reservoirs  of  warm 
water  apparently  gathered  by  trade  winds  to  subdue  the  cold 
of  the  high  latitudes,  that  much  of  the  energy  of  such  winds 
is  now  lost  to  the  world,  while  maintaining  a  vast  and  pent-up 
high  sea-level  which  has  a  difficult  outlet  to  the  northern  seas, 
and  no  strongly  attractive  low  sea-level  to  move  its  waters  into 
the  oceans  of  the  high  southern  latitudes.  The  wide  waters 
which  are  banked  up  to  the  windward  of  the  West  India 
Islands,  and  cause  the  wide  tide-rips,  set  mostly  to  the  westward 


48 

into  the  Caribbean  Sea  through  the  passages  south  of  Guade- 
loupe, while  the  northern  portion  of  the  raised  waters  set 
mostly  toward  the  north,  and  thus  form  the  eastern  boundary 
of  the  Gulf  Stream,  and  comprise  the  inner  circle  of  the  great 
current  that  encircles  the  Sargasso  Sea. 

I  have  been  informed  by  an  old  Barbuda  fisherman  that  "  the 
weeds  which  float  on  the  surface  of  the  Sargasso  Sea  grow  in 
large  quantities  on  the  bottom  of  the  shoal  waters  to  the  north 
and  eastward  of  that  island  and  Antigua."  Consequently,  the 
currents  of  that  region  carry  such  weeds  as  become  detached 
from  their  places  of  growth  into  the  higher  latitudes,  where 
the  westerly  winds  in  the  winter  season  drift  them  eastward 
south  of  Bermuda,  until  finally  the  central  area  of  their  gath- 
ering, where  the  most  dense  collection  of  weeds  is  found,  is 
situated  near  the  tropic  of  Cancer,  and  about  55°  west  longi- 
tude, as  shown  on  map  No.  2. 

This  position  is  also  the  centre  of  the  great  circular  currents 
which  encompass  the  Sargasso  Sea.  The  comparatively  few 
weeds  which  enter  the  Gulf  Stream  abreast  Florida  are  cur- 
rented  to  the  northward  of  the  Bermuda  Islands,  and  from 
thence  drifted  by  the  westerly  winds  to  the  south-west  of  the 
Azores  before  entering  the  trade-wind  belt.  The  weeds,  on 
their  long  drift  from  their  native  shoals,  hold  their  freshness, 
and  continue  to  grow  while  floating  on  the  sea  for  a  consider- 
able time,  but  at  length  lose  their  renovating  properties,  and 
in  certain  areas  of  the  sea  acquire  an  appearance  of  age  and 
decay. 

The  Gulf  Stream,  and  such  other  tropical  waters  as  are  at- 
tracted northward  to  the  low  sea-level  abreast  the  North  Ameri- 
can coast,  pass  into  the  westerly  wind-belt,  and  so  gradually 
become  drift  currents,  while  being  forced  by  the  winds  over  to 
the  European  side  of  the  ocean,  as  we  have  previously  shown. 

The  vast  movement  of  the  North  Atlantic  waters  encircling 
the  great  Sargasso  Sea  has  often  been  pointed  out  by  writers 
on  the  subject.  But  the  central  and  most  dense  portion  of  the 


49 

vast  sea  of  weeds  has  always  been  placed  on  the  charts  several 
degrees  of  longitude  east  of  its  true  position. 

It  is  fifteen  years  since  I  wrote  of  the  Gulf  Stream  and  arctic 
currents  as  being  attracted  to  a  low  sea-level  caused  by  the 
westerly  winds.  But,  as  far  as  I  know,  writers  on  the  Atlantic 
currents  have  had  nothing  to  say  of  the  great  low  sea-level 
caused  by  the  westerly  winds  blowing  the  surface  waters  of  the 
North  Atlantic  away  from  the  eastern  coast  of  North  America, 
from  Georgia  to  Newfoundland,  and  thus  attracting  the  arctic 
and  Gulf  Stream  waters  in  opposite  directions,  fifteen  hundred 
miles  along  the  North  American  coast.  For,  were  it  not  for 
this  low  sea-level,  the  Gulf  Stream  would  not  be  able  to  move 
so  far  northward  as  it  now  flows,  but  would  spread  out,  were 
there  no  unevenness  in  the  sea-level  of  the  Atlantic,  and  be- 
come a  drift  current  far  south  of  its  present  northern  limits. 
The  United  States  government  has  caused  surveys  to  be  made 
of  the  Gulf  Stream,  and  the  interesting  discoveries  thus  ob- 
tained have  all  been  laid  before  the  public.  Still,  such  sur- 
veys cover  but  a  portion  of  the  whole  round  of  the  vast  move- 
ment of  the  Gulf  Stream  water,  and  do  not  refer  to  the  vast 
high  sea-level  of  the  calm  belt  as  being  one  of  its  feeders,  or  to 
the  wide  disturbance  of  the  surface  waters  of  the  tropical 
North  Atlantic  in  their  conflict  with  the  trade  winds,  while 
being  forced  to  the  vast  high  sea-level  of  the  Caribbean  Sea 
and  Gulf  of  Mexico,  and  so  giving  head  to  the  Gulf  Stream. 

Thus  from  the  foregoing  explanations  it  will  be  seen  that  the 
ability  of  the  prevailing  winds  to  move  the  surface  waters  of 
the  ocean  away  from  the  weather  shores  of  continents  over 
against  the  opposite  leeward  shores  in  the  different  wind-belts 
of  the  globe,  and  so  cause  both  high  and  low  sea-levels,  is  the 
main  reason  why  there  is  an  interchange  of  surface  water  be- 
tween the  tropical  and  colder  zones  sufficient  to  carry  heat 
from  the  tropics  to  the  cooler  regions,  and  thus  largely  affect 
the  temperature  of  the  higher  latitudes. 

The  unmistakable  traces  of  cold  periods  having  occurred  in 


50 

both  hemispheres  have  given  rise  to  an  ingenious  astronomical 
theory  to  account  for  their  origin.  According  to  this  theory 
the  ice  periods  in  the  two  hemispheres  were  consecutive;  and 
it  is  admitted  by  its  supporters  that,  should  it  be  shown  that 
the  frigid  periods  in  the  northern  and  southern  hemispheres 
were  concurrent,  the  astronomical  doctrine  would  have  to  be 
abandoned. 

It  is  impossible  for  a  person  who  is  acquainted  with  the 
great  surface  currents  of  the  several  oceans  to  conceive  how 
a  mild  period  could  be  maintained  in  the  northern  hemisphere 
with  a  frigid  period  existing  in  the  southern  hemisphere. 
A  frigid  period  in  the  latter  hemisphere  necessitates  a  cold 
temperature  for  the  superior  oceans  of  the  globe  south  of  the 
equator.  With  this  vast  area  of  water  reduced  to  a  chilling 
temperature,  it  seems  impossible  for  the  inferior  waters  of  the 
northern  latitudes  to  maintain  sufficient  warmth  to  favor  a 
mild  period  in  the  northern  hemisphere,  especially  with  both 
hemispheres  receiving  an  equal  annual  amount  of  the  sun's 
rays.  The  great  Humboldt  current,  having  its  rise  in  the 
southern  ocean  west  of  Cape  Horn,  would  during  a  southern 
frigid  period  greatly  lower  the  temperature  of  the  vast  equato- 
rial stream  in  the  Pacific  Ocean.  Consequently,  the  Japanese 
stream,  which  branches  off  from  the  equatorial  current  into 
the  North  Pacific,  would  be  cooled  to  such  a  degree  that  it 
would  be  unable  to  maintain  the  mild  climate  on  the  shores  of 
the  North  Pacific  which  extensive  lands  now  enjoy.  Further- 
more, during  a  cold  period  in  [the  southern  hemisphere  the 
temperature  of  the  Gulf  Stream  would  also  be  greatly  lowered  by 
the  great  South-eastern  Atlantic  return  current,  which  is  caused 
by  the  south-east  trade  winds  impelling  the  surface  waters  of 
that  region  into  the  equatorial  latitudes,  such  waters  being  re- 
plenished from  the  common  level  of  the  southern  ocean,  and 
so  mingling  the  cool  waters  of  that  sea  with  the  equatorial 
waters  of  the  Atlantic  during  a  frigid  period  in  the  southern 
latitudes.  And  it  may  be  said  that  during  such  times  the 


51 

frigid  Antarctic  Ocean  would  send  its  cold  under-currents  to 
cool  the  inferior  northern  oceans.  Even  to-day  the  northern 
and  southern  hemispheres,  through  the  intermingling  of  the 
waters  of  the  northern  and  southern  oceans,  largely  maintain 
a  like  temperature  in  their  temperate  zones.  Therefore,  when 
we  consider  the  certain  traces  of  ice-sheets  having  formed  on 
South  Africa  and  Southern  Australia,  and  to  have  overrun 
South  America  above  the  latitude  of  40°  south,  thus  strewing 
the  oceans  of  the  southern  temperate  zone  with  ice  that  are 
now  largely  free  from  it,  it  seems  that  the  maintenance  of 
warm  oceans  in  the  northern  hemisphere  during  the  time  of  a 
frigid  period  in  the  southern  hemisphere  would  be  impossible. 

In  order  to  make  this  statement  more  plain,  I  will  again 
refer  to  the  importance  of  the  great  Humboldt  current  for 
cooling  the  waters  of  the  North  Pacific  during  the  perfection 
of  a  southern  ice  age.  For  during  such  times  the  ocean 
strewed  with  ice  west  of  Cape  Horn,  where  the  Humboldt 
current  takes  its  rise,  would  impart  its  coldness  to  the  Hum- 
boldt stream,  while  it  was  floating  icebergs  toward  the  equator. 
The  equatorial  current  of  the  Pacific  being  a  continuation  of 
the  Humboldt  stream,  its  waters  would  partake  of  its  coldness. 
The  Japanese  current,  being  a  large  offshoot  from  the  equato- 
rial stream,  would  also  possess  a  lower  temperature  than  it 
obtains  at  this  age.  Yet  at  this  date,  with  the  southern  ice- 
sheets  confined  to  the  antarctic  lands,  it  does  not  possess  heat 
sufficient  to  prevent  glaciers  from  flowing  down  to  the  tide- 
water from  mountains  in  Alaska. 

Consequently,  the  Japanese  stream  could  not  maintain  a 
mild  climate  on  the  North  Pacific  coasts  while  a  cold  period 
was  being  completed  in  the  southern  hemispheres.  Therefore, 
under  the  conditions  above  set  forth  the  support  of  a  mild 
period  in  the  northern  hemisphere  during  the  existence  of  a 
frigid  period  in  the  southern  hemisphere  could  not  be  carried 
out. 

From  what  has  been  explained,  it  will  be  seen  that  the 


52 

growth  of  an  ice  period  is  necessarily  slow,  especially  in  its 
early  stage,  and  also  that  the  storage  of  ice  is  carried  on  in 
both  hemispheres  at  the  same  time;  but  I  will  call  further 
attention  to  the  southern  hemisphere,  because  it  possesses 
greater  resources  than  the  northern  for  the  production  of  an 
ice  age. 

The  independent  circulation  of  the  southern  ocean  waters, 
as  before  shown,  turns  away  the  tropical  currents,  and  thus 
largely  prevents  their  warm  waters  from  entering  the  high 
southern  latitudes.  Consequently,  the  heat  •  from  the  sun's 
rays,  and  all  other  sources  of  heat  included,  are  not  suffi- 
cient to  prevent  ice  from  gathering  on  lands  within  the  ant- 
arctic circle.  This  increasing  storage  of  ice  is  only  another 
name  for  the  accumulation  and  spreading  of  cold,  and  so  the 
increasing  dullness  goes  on.  The  snow  falls,  and  thus  adds 
to  the  extension  and  thickness  of  the  ice-sheets;  and  at  the 
same  time  the  spreading  snow-fields  reflect  the  heat  received 
from  the  sun's  rays  into  space,  while  the  cold  is  retained  and 
increased  in  the  growing  glaciers. 

The  spreading  ice-sheets  having  covered  the  land  are  able 
to  flow  into  the  surrounding  seas,  where  their  outer  edges 
become  detached  and  form  icebergs,  which  float  out  to  sea,  and 
so  scatter  over  the  adjoining  oceans.  Thus  their  coldness  is 
mingled  with  and  largely  preserved  by  the  sea,  while  the  sur- 
face water,  which  is  carried  into  the  southern  latitudes  from 
the  northern  oceans  by  the  prevailing  winds,  and  also  such 
surface  waters  as  are  attracted  into  the  antarctic  seas  because 
of  the  difference  of  temperature  of  the  antarctic  waters  and 
the  more  northern  seas,  are  on  gaining  the  frigid  latitudes 
made  cool,  and  returned  to  the  more  northern  seas  in  cold 
under-currents,  and  so  chilling  the  vast  under-waters  of  the 
great  oceans  of  the  globe,  and  eventually  their  wide  surface 
waters  also ;  and  so  the  coldness  increases  until  the  ice-sheets 
which  at  first  formed  on  polar  lands  are  enabled  to  spread 
slowly  toward  the  equatorial  regions  so  long  as  the  indepen- 
dent circulation  of  the  southern  ocean  is  maintained. 


53 

But  at  length  the  depth  of  the  great  southern  ocean  is  dimin- 
ished because  of  the  water  evaporated  from  its  surface,  and 
precipitated  in  the  shape  of  hail  and  snow  over  the  vast  conti- 
nents and  islands  of  the  high  northern  latitudes,  thus  add- 
ing sufficient  weight  to  the  northern  lands  to  attract  the  waters 
of  the  southern  seas  and  still  further  lessen  their  depth.  Thus 
during  such  times  the  Cape  Horn  channel  is  so  reduced  as  to  be 
obstructed  by  the  heavy  glaciers  and  icebergs  of  an  ice  age. 

Consequently,  a  great  change  is  wrought  in  the  circulation  of 
the  southern  seas.  For,  when  the  Cape  Horn  channel  is  closed, 
the  westerly  winds  employ  their  strength  to  force  the  ocean's 
surface  waters  away  from  the  glaciers  which  have  filled  the 
diminished  channel.  This  potent  action  of  the  winds  necessa- 
rily creates  a  great  low  sea-level  on  the  Atlantic  side  of  the  ob- 
structed strait,  sufficient  to  attract  the  tropical  waters  heaped 
against  Brazil  by  the  trade  winds,  and  the  waters  of  the  high 
sea-level  of  the  equatorial  calm  belt,  and  also  the  equatorial 
waters  which  set  along  the  east  coast  of  Africa,  well  into  the 
southern  seas. 

It  will  thus  be  seen  that  the  conditions  for  the  circulation  of 
the  tropical  ocean  waters  have  met  with  a  great  change. 

But  the  temperature  of  the  waters  has  been  lowered  by  the 
coldness  of  a  frigid  period ;  and,  consequently,  their  capability 
for  conveying  heat  to  the  high  latitudes  has  largely  dimin- 
ished. Therefore,  their  first  inroads  in  the  higher  latitudes 
make  small  impression  on  the  icy  seas,  so  the  early  process  for 
melting  ice  is  exceedingly  slow.  But  the  icy  southern  ocean, 
deprived  of  its  independent  circulation,  in  the  course  of  time 
yields  to  the  warming  invasion  of  the  tropical  waters,  whose 
wide  and  increasing  spread  is  eventually  able  to  bring  about  a 
mild  period,  according  to  the  natural  methods  which  I  have  ex- 
plained in  the  preceding  pages. 

And  it  may  be  said  that  a  mild  period  succeeding  a  glacial 
age  gained  sufficient  warmth  to  melt  the  ice-sheets  from  all 
lands  excepting  the  highest  mountains.  For  it  is  probable 


54 

that  there  are  lands  situated  in  the  antarctic  circle  sufficiently 
elevated  even  during  late  Tertiary  times  to  have  been  above 
the  snow-line.  Therefore,  the  glaciers  on  such  lands  could  not 
have  melted  away  during  mild  periods  succeeding  an  ice  age. 
For,  as  has  been  explained,  a  portion  of  the  waters  of  the  south- 
ern seas  had  moved  into  the  northern  hemisphere.  Conse- 
quently, the  antarctic  lands  were  raised  higher  above  the  sea- 
level  than  at  this  age.  Hence  the  area  of  lofty  land  was  in- 
creased above  the  snow-line.  And,  according  to  Dr.  James 
Croll's  estimate,  the  ice-sheet  at  the  south  pole  is  at  this  age 
several  miles  in  thickness.  Therefore,  its  upper  surface  is 
above  the  line  of  perpetual  snow,  and  could  not  be  melted 
away  during  the  warm  eras  succeeding  glacial  periods. 


CHAPTER  III. 

THE  SPREAD  OF  GLACIERS  DURING  COLD  EPOCHS. 

I  HAVE  before  explained  that  the  conditions  are  such  that 
the  cold  periods  of  the  northern  and  southern  hemispheres 
were  concurrent.  Through  this  cause,  while  the  glacial  epoch 
was  being  perfected,  the  ice  followed  down  the  mountain 
ranges  of  both  hemispheres ;  and,  while  gathering  on  the  lands 
of  the  temperate  latitudes,  it  also  spread  over  a  portion  of  the 
tropical  zone.  It  is  reported  that  traces  of  ancient  glaciers  are 
found  in  India,  and  also  in  Central  America  and  in  tropical 
South  America.  In  fact,  the  denudation  caused  by  ancient 
glaciers  on  the  elevated  lands  of  the  tropics  are  too  well  de- 
fined to  be  attributed  to  any  process  of  weathering,  while  Al- 
pine plants  of  the  same  species  are  found  near  the  summits  of 
mountains  in  the  tropics  as  well  as  in  the  high  latitudes  of 
both  hemispheres. 

This  fact  goes  to  show  that  a  portion  of  the  lowlands  of  the 
tropical  zone  have  experienced  a  temperature  favorable  for  the 


55 

growth  of  Alpine  plants.  And,  judging  from  the  tropical 
islands  I  have  visited,  situated  in  the  cold  currents  which  flow 
down  the  eastern  sides  of  the  oceans  from  the  high  latitudes,  I 
think  they  show  strong  traces  of  having  during  some  remote 
period  been  subject  to  the  action  of  glaciers.  The  island  of  St. 
Helena,  situated  in  the  southern  tropical  Atlantic,  has  the  ap- 
pearance of  having  been  heavily  iced  during  a  frigid  age.  Its 
steep  ravines,  which  deepen  as  they  approach  the  sea,  recall  to 
the  southern  voyager  the  ice-worn  islands  of  the  high  latitudes. 
It  seems  improbable  that  these  deep  ravines  which  penetrate 
the  hard  volcanic  rock,  on  their  short  course  to  the  sea,  could 
have  been  caused  by  their  scanty  brooklets. 

The  bowlders  scattered  over  the  island  are  not  in  harmony 
with  the  weathering  process,  while  the  obliteration  of  its 
craters  seems  to  point  to  a  more  rapid  process  of  erosion  than 
could  be  attributed  to  weathering. 

Professor  Agassiz,  in  his  "  General  Sketch  of  the  Expedition 
of  the  '  Albatross,' "  states  that  the  Galapagos  Islands  are  of 
volcanic  origin,  and  that  their  age  does  not  reach  beyond  the 
earliest  Tertiary  period ;  and  his  report  seems  to  favor  the  im- 
pression of  their  having  undergone  denudation  sufficient  to 
slough  off  large  portions  of  the  rims  of  the  older  craters,  and 
also  the  eastern  face  of  Wenman  Island.  On  Hood's  Island, 
at  the  time  of  my  visit,  its  crater  had  entirely  disappeared. 

The  highest  portion  of  the  island,  which  was  the  probable  site 
of  its  ancient  crater,  showed  no  trace  of  its  former  existence ; 
yet  at  the  foot  of  this  low  mountain,  on  its  southern  side,  I  saw 
a  large  collection  of  loose  bowlders,  composed  of  hard  volcanic 
rock,  which  were  mostly  free  from  soil  and  other  debris,  and 
easily  moved  from  their  places,  while  the  spaces  afforded  by 
the  loose  piles  of  dark  basaltic  rocks  afforded  a  secure  retreat 
for  numerous  owls  and  lizards.  Beyond  the  rocky  piles  to  the 
southward  a  horizontal  area  of  land  was  strewn  with  bowlders 
to  the  sea,  which  was  some  two  miles  distant  from  the  higher 
land.  The  bowlders  which  covered  the  plain  were  somewhat 


56 

smaller  than  those  at  the  foot  of  the  mountain,  as  none  of  the 
former  were  more  than  three  or  four  feet  in  their  longest  meas- 
urement. 

They  seem  to  have  been  formed  from  thin  strata  of  lava, 
which  were  broken  in  pieces  from  pressure,  such  as  the  action 
of  ice  could  perform.  In  fact,  the  crowded  and  angular  and 
somewhat  worn  blocks  of  lava  presented  a  different  appearance 
from  stones  thrown  from  the  crater  of  a  volcano,  while  no  such 
bowlders  are  found  among  the  recent  volcanic  eruptions  on  the 
islands. 

The  plain  so  thickly  strewn  with  bowlders,  and  partly 
shaded  by  a  tall  growth  of  shrubs,  fell  off  abruptly  at  the  sea- 
side, forming  a  steep  cliff  some  two  hundred  feet  in  height. 

The  rocky  floor  at  the  foot  of  the  cliff  received  such  debris  as 
fell  from  the  sea-washed  land  ;  yet  it  contained  few  bowlders, 
they  having  been  washed  away  by  the  waves  soon  after  falling. 

At  one  place  a  steep,  dry  ravine  penetrated  the  land  from  the 
seashore,  which  was  dangerous  to  cross  on  account  of  the  loose 
stones  resting  on  its  sides.  Two  or  three  miles  further  west, 
on  the  level  land  bordering  the  sea,  a  large  rookery  of  albatross 
were  brooding  their  eggs  and  chicklings.  The  land  on  the 
south  side  of  Albemarle,  near  the  sea,  consists  of  debris  from 
the  eroded  high  lands  ;  and,  judging  from  the  crumbling  cliffs 
by  the  sea,  it  seems  that  the  land  at  one  time  extended  further 
seaward. 

Besides  the  excessive  denudation  which  appears  to  have 
taken  place  on  portions  of  these  bowlder-strewn  lands,  we  have 
other  unmistakable  testimony  of  their  having  formerly  pos- 
sessed a  frigid  temperature.  The  characteristic  Alpine  flora  of 
these  islands  points  to  a  time  when  they  were  exposed  to  a  cold 
climate.  Furthermore,  rookeries  of  seal  and  albatross,  which 
naturally  belong  to  shores  situated  in  cold  latitudes,  still  exist 
on  these  equatorial  islands ;  and,  when  we  consider  the  favor- 
able position  of  the  Galapagos  for  the  reception  of  cold  during 
a  frigid  period,  we  can  well  account  for  the  lingering  signs 
which  point  to  their  former  cold  climate. 


57 

During  the  perfection  of  an  ice  period  the  western  shore  of 
South  America  was  covered  with  an  ice-sheet  from  the  summits 
of  its  mountain  range  to  the  sea,  extending  northward  as  far  as 
the  latitude  of  38°  south. 

This  vast  ice-sheet,  situated  in  a  region  of  great  snow-fall, 
was  constantly  sending  icebergs  into  the  sea,  where  they  were 
borne  northward  by  the  cold  Humboldt  current  directly  toward 
the  Galapagos  Islands  ;  while,  on  the  other  hand,  in  the  north- 
ern latitudes,  in  regions  of  great  snow-fall,  such  as  Alaska  and 
British  America,  numerous  icebergs  were  launched  into  the 
ocean,  to  be  currented  southward  to  the  Galapagos  seas.  Thus 
during  the  frigid  epoch  the  equatorial  waters  surrounding  the 
Galapagos  group  was  one  of  the  greatest  gathering  places  for 
floating  ice  to  be  found  on  the  globe. 

And  here  the  frigidity  stored  up  in  the  glaciers  of  the  higher 
latitudes  was  set  free,  thus  chilling  the  waters  as  well  as  the 
atmosphere  of  that  region.  The  Alpine  flora  of  the  American 
coast  mountains  was  probably  carried  by  floating  ice  to  the 
Galapagos,  while  its  rookeries  of  albatross  and  seal  date  back 
to  a  cold  period.  And  it  seems  that  these  cold-weather  ani- 
mals, with  the  assistance  of  the  cool  Humboldt  current,  may  be 
able  to  preserve  their  rookeries  at  the  equator  until  the  advent 
of  another  ice  period.  In  connection  with  the  evidences  of  a 
cold  climate  having  possessed  the  Galapagos,  there  are  ample 
traces  of  ice-sheets  having  flowed  over  a  large  portion  of  the 
high  lands  of  tropical  America,  and  in  some  places  the  ice  may 
have  flowed  down  to  the  sea,  especially  where  the  large  rivers 
now  empty;  and  it  is  said  that  masses  of  clay,  mixed  with  sub- 
angular  stones,  have  been  found  in  Brazil,  which  goes  to  prove 
the  glaciation  of  portions  of  that  tropical  land  during  a  remote 
age.  Professor  Louis  J.  R.  Agassiz,  during  his  research  in  the 
Amazon  valley,  found  bowlders  resting  near  the  summits  of  the 
low  hills  of  that  region,  which  he  attributed  to  the  action  of 
ice.  The  spread  of  glaciers  on  southern  continents  and  islands 
is  shown  on  map  No.  1. 


58 

In  Science,  Nov.  17,  1893,  Mr.  J.  Crawford  published  a  sum- 
mary of  his  discoveries  in  Nicaragua,  during  ten  months  of 
nearly  continuous  exploration  since  August,  1892. 

The  author  of  this  report  says :  "  The  numerous  eroded 
mountain  ridges  and  lateral  terminal  moraines  of  that  tropical 
region  give  unquestionable  evidences  of  the  former  existence 
of  a  glacial  epoch,  which  covered  an  area  of  several  thousand 
square  miles  in  Nicaragua  with  glacial  ice.  The  ice-sheet 
covered  a  large  part  of  the  existing  narrow  divide  of  land 
(containing  about  48,000  square  miles)  between  the  Pacific  and 
Caribbean  Sea."  And  it  is  likely  that  other  large  areas  of  trop- 
ical America  were  glaciated  at  the  same  time,  especially  in 
regions  of  great  precipitation. 

The  island  of  Cuba,  during  a  portion  of  the  ice  age,  probably 
supported  heavy  glaciers,  and  obtained  an  average  temperature 
as  low  as  South-western  New  Zealand  at  this  age.  According 
to  the  description  given  by  J.  W.  Spencer,  of  the  Cuban  land, 
great  valleys  have  been  excavated,  the  lower  portion  of  which 
are  now  fiords,  reaching  in  one  case  at  least  to  seven  thousand 
feet  in  depth  before  gaining  the  sea  beyond.  Thus,  while  keep- 
ing in  view  the  glacial  condition  of  Central  America  during  the 
frigid  period,  it  seems  that  the  great  Cuban  excavations  were 
partly  the  work  of  glaciers  of  the  same  cold  epoch.*  Judging 
from  such  reliable  statements,  it  is  probable  that  the  climate  of 
tropical  America  during  the  frigid  age  was  somewhat  colder  than 
obtained  in  the  tropical  regions  of  the  eastern  continent,  owing 
to  the  wide  connection  of  the  Atlantic  with  the  Arctic  Ocean 
as  well  as  with  the  antarctic  seas,  and  because  of  its  shores  pos- 

*The  meeting  of  the  British  Association  for  the  Advancement  of 
Science,  September,  1895,  was  reported  in  Science  of  October  18,  where 
mention  is  made  of  an  interesting  paper  by  Mr.  R.  B.  White,  on  "  The 
Glacial  Age  of  Tropical  America,"  in  which  he  described  a  number  of 
apparently  glacial  deposits  in  the  Republic  of  Colombia,  almost  under  the 
equator.  He  spoke  of  moraines  forming  veritable  mountains,  immense 
thicknesses  of  bowlder  clay,  breccias,  cement  beds,  sand,  gravels,  and 
clays,  beds  of  loess,  valleys  scooped,  grooved,  and  terraced,  monstrous 
erratics,  and  traces  of  great  avalanches." 


59 

sessing  a  larger  area  of  glaciated  lands  in  proportion  to  its 
size  than  the  Pacific  and  Indian  Oceans,  and  also  owing  to  the 
tropical  Atlantic  containing  so  small  a  portion  of  the  world's 
waters  which  lie  within  the  torrid  zone,  and  its  equatorial  cur- 
rent being  separated  by  continental  lands  from  the  great  equa- 
torial stream  of  the  Pacific  and  Indian  Oceans. 

Therefore,  the  tropical  Atlantic  waters  must  have  been  re- 
duced to  a  lower  temperature  during  a  frigid  age  than  the 
tropical  waters  of  the  Indian  Ocean  or  the  western  part  of  the 
tropical  Pacific,  as  a  large  portion  of  the  great  equatorial  cur- 
rent of  the  latter  oceans,  during  its  western  movement,  was  ex- 
posed to  the  rays  of  a  tropical  sun  for  a  much  longer  time,  after 
being  replenished  by  the  cold  waters  of  the  high  latitudes,  than 
the  tropical  currents  of  the  Atlantic ;  and  it  is  probable  that, 
on  account  of  tropical  America  possessing  a  colder  climate  than 
the  tropical  lands  of  the  eastern  continent  during  the  frigid 
epoch,  the  cold  of  the  western  continent  was  more  destructive 
to  its  fauna  and  flora  than  was  the  case  in  the  tropical  regions 
of  the  eastern  continent.  Professor  Wright,  in  his  valuable  work 
on  "  The  Ice  Age  of  North  America,"  gives  a  good  description 
of  the  "  flight  of  plants  and  animals  during  the  glacial  epoch," 
and  also  of  the  extermination  of  many  superior  species  because 
of  the  frigid  climate. 

The  high  lands  of  tropical  Africa,  above  the  altitude  of 
three  thousand  feet,  and  situated  in  places  of  great  precipita- 
tion, were  probably  covered  with  snow  and  ice  during  the 
glacial  age.  Travellers  have  reported  that  islands  composed 
partly  of  granite  bowlders  are  found  in  the  lakes  at  the  head- 
waters of  the  Nile.  But  the  glaciers  that  invaded  the  tropical 
latitudes  were  of  short  duration  compared  with  the  ice-sheets 
that  burdened  the  lands  of  the  temperate  zones.  Besides,  such 
tropical  ice  as  flowed  to  the  low  lands  was  so  near  a  melting 
condition  that  it  made  small  impression  on  the  rocks ;  but  on 
steep  mountain  slopes,  where  the  movement  of  the  ice  was 
comparatively  rapid,  it  possessed  considerable  eroding  power. 


60 

The  climate  of  the  tropical  zone  on  both  continents  during  the 
perfection  of  an  ice  period  was  so  cold  that  such  animals  as 
could  not  endure  a  low  temperature  retreated  into  the  warmest 
regions  of  the  equatorial  latitudes,  while  many  species  who 
failed  to  reach  such  places  perished.  And  especially  was  this 
the  case  with  the  pre-glacial  fauna  of  the  western  continent. 
Mr.  W.  B.  M.  Davidson,  in  his  treatise  on  Florida  phosphates, 
says :  "  The  great  mammal  hordes  of  the  glacial  epoch  were 
driven  into  Florida  in  their  flight  southward  for  life  aud 
warmth,  and  there  perished  because  of  the  deadly  cold  which 
ever  moved  southward.  The  Florida  waters  grew  so  icy  cold, 
fishes,  reptiles,  and  mammoth  animals  died,  and  added  their 
frames  and  teeth  to  the  valley  of  bones  now  found  in  that 
southern  region." 

Such  species  of  the  tropical  fauna  of  the  ocean  as  survived 
the  ice  age  could  have  existed  only  in  torrid  seas  with  small 
connection  with  the  cold  oceans  during  the  frigid  epochs.  For, 
with  the  diminished  oceans  of  a  cold  period,  it  seems  that 
the  conditions  were  favorable  for  the  maintenance  of  such 
seas  in  the  region  of  the  East  India  Islands. 

Such  parts  of  Southern  Europe  and  Northern  Africa  as 
bordered  on  the  Mediterranean  Sea  probably  possessed  a 
milder  climate  during  the  ice  age  than  regions  in  the  same 
latitudes  on  the  Atlantic  coast,  for  the  reason  that  the  North 
Atlantic  was  proportionally  a  greater  receptacle  for  icebergs 
which  were  launched  into  it  from  the  numerous  glaciers  of 
North-eastern  America,  Greenland,  Iceland,  and  North-western 
Europe  than  the  great  inland  sea  obtained  from  its  less  frigid 
shores.  And  it  may  have  happened  that  during  such  times  the 
tropical  waters  of  the  Indian  Ocean  had  some  connection  with 
the  Mediterranean  through  the  Red  Sea  and  Suez,  and  so  dur- 
ing portions  of  the  year  the  waters  of  the  tropical  Indian 
Ocean  were  forced  by  the  periodical  winds  into  the  inland  sea. 
It  is  the  opinion  of  several  writers  that  man,  along  with  other 
species  of  animal  life,  existed  previous  to  the  glacial  period ; 


61 

for,  since  the  seas  and  lands  of  the  globe  were  chilled,  the  con- 
ditions seem  to  have  been  less  favorable  for  the  spontaneous 
generation  of  animate  bodies  than  during  the  previous  warm 
ages.  Therefore,  it  appears  that  the  generative  ages  should 
be  ascribed  to  the  long  genial  eras  prior  to  the  glacial  epochs. 
For  it  is  probable  that  the  lower  parts  of  the  ocean,  which 
now  possess  a  low  temperature  even  in  the  tropical  latitudes, 
were,  during  the  warm  eras,  wholly  composed  of  warm  water, 
because  the  surface  waters  of  the  antarctic  seas  of  that  age, 
which  supply  the  great  under-currents  of  the  ocean,  would 
possess  a  high  temperature ;  and  it  is  probable  that  the  tem- 
perature of  a  large  portion  of  the  seas  of  the  torrid  zone  was 
for  a  long  time  maintained  at  blood  heat.  For  it  should  be 
considered  that  the  waters  which  moved  from  the  torrid  seas, 
after  making  their  journey  through  the  warm  regions  of  the 
high  latitudes,  would  on  their  return  to  the  tropics  retain  a 
large  portion  of  the  heat  they  acquired  in  the  torrid  zone  before 
making  their  journey  to  the  mild  polar  regions. 

And,  when  we  reflect  how  the  heat  of  the  sun's  rays  was 
conserved  by  the  ocean  waters,  and  that  their  circulation  dur- 
ing such  times  was  almost  wholly  performed  by  the  winds,  as 
the  difference  of  temperature  between  the  polar  latitudes  and 
the  equator  was  small,  it  appears  that  during  the  eras  previous 
to  the  glacial  age  the  oceans  must  have  obtained  a  higher 
temperature  than  possessed  by  the  warmest  seas  of  to-day. 

According  to  the  discoveries  of  Professor  Wright  and  others, 
ancient  stone  implements  have  been  found  beneath  the  glacial 
drift,  as  well  as  the  bones  of  animals  whose  descendants  are 
now  living,  which  goes  to  prove  that  man,  with  other  species  of 
fauna  which  now  inhabit  the  earth,  existed  anterior  to  the 
glacial  epoch. 

And  on  consideration  it  seems  unreasonable  to  suppose  that 
any  of  the  superior  species  of  animals  could  have  been  brought 
into  existence  since  the  waters  and  lands  of  the  earth  were 
chilled  by  the  cold  of  a  glacial  age.  And  it  appears  that  many 


62 

species  of  animals  which  are  known  to  have  survived  the  cold 
periods  were  indebted  for  such  survivals  to  the  slow  process 
through  which  a  frigid  period  is  brought  about,  thus  affording 
time  for  evolutionary  inurement  to  the  slow  increase  of  cold 
which  at  length  perfects  a  glacial  epoch. 

The  inurement  to  cold  acquired  by  animals  during  the 
glacial  age  is  still  an  attribute  possessed  by  many  species 
of  fauna  to-day.  For,  when  a  warm  climate  took  possession  of 
the  tropical  zone,  it  was  deserted  by  a  large  portion  of  the 
animals  that  found  refuge  there  during  the  glacial  age. 

Thus,  while  the  seas  and  shores  of  the  cooler  latitudes  swarm 
with  animate  bodies,  the  torrid  latitudes  seem  comparatively 
lonely  to  the  voyagers  on  the  tropical  oceans. 


CHAPTER  IV. 

THE   GLACIERS    OF    THE   TEMPERATE   ZONES. 

HAVING  asserted  that  during  the  culmination  of  a  frigid 
period  the  ice-sheets  spread  over  a  portion  of  the  lands  of  the 
tropical  zone,  I  will  give  my  views,  with  those  of  several 
writers,  on  the  spread  of  ice-sheets  within  the  now  temperate 
latitudes ;  and  meanwhile  I  will  repeat  a  portion  of  my  former 
essays  on  the  subject.  Professor  Hitchcock,  in  his  lectures  on 
the  early  history  of  North  America,  says  that  "  the  history  opens 
with  igneous  agency  in  the  ascendant,  aqueous  and  organic 
forces  become  conspicuous  later  on,  and  ice  has  put  on  the 
finishing  touches  to  the  terrestrial  contours."  But  there  appear 
to  be  various  opinions  held  by  geologists  respecting  the  changes 
brought  about  on  the  earth's  surface  during  the  glacial  period. 
Some  think  that  glaciers  have  never  been  an  important  geologi- 
cal agent,  while  others  assert  that  during  the  glacial  epoch 
heavy  ice-sheets  covered  the  elevated  portions  of  Western 


63 

North  America  as  far  south  as  the  thirty-sixth  parallel  of  lati- 
tude, and  Eastern  North  America  was  overspread  with  ice- 
sheets,  which  attained  a  depth  of  five  or  six  thousand  feet,  and 
were  able  to  more  their  debris  over  wide  lands  of  little  declivity 
toward  the  sea,  their  immense  deposits  forming  the  lands 
of  Cape  Cod,  and  also  the  islands  of  Nantucket  and  Martha's 
Vineyard. 

But  it  is  now  said  that  thia  implied  magnitude  of  the  glacial 
deposits  on  the  lands  skirting  the  New  England  coast  is  with- 
out foundation,  since  the  larger  bulk  of  these  islands  consists 
of  upturned  Cretaceous  and  Tertiary  strata,  which  are  only 
thinly  covered  with  glacial  debris,  such  as  bowlders,  gravel, 
clay,  and  sand,  from  the  eroded  shores  of  the  mainland  of 
New  England.  But  it  appears  that  the  dislocated  and  folded 
cretaceous  strata  which  underlie  the  glacial  drift  of  Nantucket 
and  Martha's  Vineyard  were  during  an  early  period  deposited 
on  the  bottom  of  a  shallow  sea,  which  then  covered  the  Vine- 
yard Sound,  Buzzard's  Bay,  and  their  surrounding  lowlands. 
Thus  the  ice-sheets  of  the  frigid  age  which  moved  over  New 
England  displaced  the  yielding  stratified  deposits  of  the  shal- 
low sea,  and  forced  them  southward  in  a  disturbed  condition  to 
the  position  which  they  now  occupy. 

Still,  it  is  apparent  that  only  a  small  portion  of  the  glacial 
drift  is  found  on  these  islands,  which,  according  to  appearances, 
must  have  been  eroded  and  moved  southward  from  the  rocky 
lands  of  New  England  during  the  ice  age ;  but  there  is  suffi- 
cient to  show  that  large  quantities  of  such  debris  were  carried 
over  the  islands  into  the  Atlantic.  And,  judging  from  the 
eroded  rocky  New  England  lands,  there  must  have  been  suffi- 
cient glacial  drift  moved  over  Nantucket  and  Martha's  Vine- 
yard into  the  ocean  beyond  to  far  exceed  in  bulk  the  deranged 
Tertiary  and  Cretaceous  deposits  which  now  form  so  large  a 
portion  of  the  islands. 

For,  when  we  look  over  lands  bearing  traces  of  the  ice  age, 
where  the  glaciers  did  not  move  their  drift  into  the  sea,  so  the 


64 

terminal  moraines  of  such  glaciers  can  be  better  estimated,  we 
can  realize  the  great  work  that  has  been  performed  by  the  ice- 
sheet  that  overran  New  England  during  a  frigid  age. 

Professor  James  Geikie.  states,  in  his  discussion  on  the  gla- 
cial deposits  of  Northern  Italy,  that  the  deposits  from  Alpine 
glaciers  of  a  frigid  period  "rise  out  of  the  plains  of  Piedmont 
as  steep  hills  to  a  height  of  fifteen  hundred  feet,  and  in  one 
place  to  nearly  two  thousand  feet.  Measured  along  its  outer 
circumference,  this  great  morainic  mass  is  found  to  have  a 
frontage  of  fifty  miles,  while  the  plain  which  it  encloses  ex- 
tends some  fifteen  miles  from  Andrate  southward."  And  it  is 
reported  that  there  are  found  on  the  southern  flank  of  the  Jura 
numerous  scattered  bowlders,  all  of  which  have  been  carried 
from  the  Alps  across  the  intervening  plains,  and  left  where 
they  now  rest.  Many  contain  thousands  of  cubic  feet,  and  not 
a  few  are  quite  as  large  as  cottages. 

Such  blocks  are  found  on  the  Jura,  at  a  height  of  no  less  than 
two  thousand  feet  above  the  Lake  of  Neuchatel.  The  Jura 
Mountains  being  formed  of  limestone,  it  is  easy  to  distinguish 
the  debris  deposited  by  Alpine  glaciers ;  and,  from  what  I  can 
learn  of  extensive  glacial  work,  it  appears  that  intervening 
plains,  lakes,  and  sounds  are  so  often  found  separating  the 
source  of  ancient  glaciers  from  their  deposits  that  their  exist- 
ence becomes  almost  necessary  to  represent  the  general  outlines 
of  disturbance  performed  during  an  ice  period.  In  consider- 
ation of  such  facts  and  the  foregoing  statements  of  reliable  ob- 
servers, I  am  prompted  to  offer  my  views  on  glacial  work  per- 
formed on  a  portion  of  the  Pacific  shores  of  North  America, 
which  seems  to  me  to  be  much  more  extensive  than  hitherto 
supposed. 

Professor  Whitney  describes  the  coast  mountains  of  Califor- 
nia as  being  made  up  of  great  disturbances,  which  have  been 
brought  about  within  geologically  recent  times ;  and  this  state- 
ment I  found  to  be  so  obvious  in  my  travels  over  that  region 
that  it  appears  to  me  that  the  coast  ranges  originated  in  a  dif- 


65 

ferent  manner  from  the  older  Sierras.  The  western  sides  of 
the  latter  mountains  everywhere  show  the  great  eroding  power 
of  ancient  glaciers  ;  and,  when  I  considered  their  favorable  po- 
sition for  the  accumulation  of  snow  during  a  glacial  period,  I 
was  led  to  seek  for  the  glacial  deposits  adequate  to  represent 
the  great  gathering  of  ice  which  an  age  of  frigid  temperature 
would  produce. 

But  it  seemed  to  me  that  such  deposits  could  not  be  found  in 
the  foot-hills  of  the  Sierras,  which  contain  the  moraine  of  infe- 
rior ice-sheets  that  terminated  at  the  base  of  the  mountains. 

Under  these  conditions  I  came  to  the  conclusion  that  during 
the  earlier  ice  period  the  immense  glaciers  which  must  have 
formed  on  the  western  slopes  of  the  Sierra  range  moved  their 
gigantic  accumulation  of  debris  so  far  seaward  as  to  form  the 
range  of  hills  now  existing  next  the  coast  line,  and  perhaps 
the  islands  abreast  the  Santa  Barbara  coast,  the  Contra  Costa, 
or  eastern  range,  being  formed  during  a  subsequent  ice  period, 
in  the  same  manner  as  the  hills  next  the  coast  line. 

Still,  it  may  be  that  neither  of  the  coast  ranges  was  the  work 
of  a  single  cold  epoch ;  but  the  western  range  must  necessarily 
have  been  the  earliest  deposit.  Although  the  coast  ranges  dif- 
fer from  the  Sierras  in  their  make  up,  yet  it  does  not  disagree 
with  the  glacial  origin  of  the  former  inferior  mountains,  from 
the  fact  that  the  ice-sheets,  while  moving  their  bulk  westward, 
displaced  the  deposits  of  such  bays,  lakes,  rivers,  and  marshes 
as  lay  abreast  of  the  Sierra  slopes.  The  advancing  ice-sheets, 
thousands  of  feet  in  depth,  moving  from  a  lofty  and  steep  in- 
cline, pressed  and  ploughed  below  the  somewhat  superficial  cre- 
taceous and  alluvial  strata  which  lay  in  their  course.  The  dis- 
turbed strata,  while  forced  along  in  confused  heaps  in  front  of 
the  ice,  were  amassed  in  ridges  sufficient  to  form  the  hills  of 
the  coast  ranges.  The  bowlders  found  imbedded  in  several  of 
the  coast  hills  must  have  been  moved  by  the  ice  from  the  Sier- 
ras on  account  of  the  coast  ranges  not  having  a  rocky  core  of 
sufficient  firmness  to  give  shape  to  such  bowlders.  Moreover, 


66 

the  temperature  of  the  Pacific  waters  would  not  be  favorable 
for  glaciers  to  form  on  the  coast  ranges,  with  the  ice-sheets  of 
the  Sierras  terminating  at  the  foot-hills. 

The  Sacramento  and  San  Joaquin  Valleys  are  now  covered 
by  recent  river  deposits.  Therefore,  the  glacial  drift  which 
should  be  traced  from  the  Sierras  to  the  coast  ranges  is  con- 
cealed. 

Yet  the  abraded  appearance  of  exposed  solid  rocks  at  the 
base  of  the  foot-hills,  and  also  the  scattered  bowlders  which 
gradually  disappear  beneath  the  diluvial  deposits  of  the  plains, 
indicate  that  the  Sierra  ice-sheets  could  not  have  ended  at  the 
foot-hills,  but  must  have  moved  further  westward,  while  gath- 
ering immense  accumulations  in  their  front,  sufficient  to  form 
the  coast  hills,  the  debris  thus  amassed  being  able  to  arrest  the 
further  movement  of  the  ice  seaward. 

The  coast  ranges  in  several  places  have  been  subject  to  igne- 
ous action,  which  may  have  been  brought  about  through  heat 
generated  from  pressure  exerted  on  the  interior  masses  after 
the  ice  had  melted  away,  the  heat  thus  produced  being  suffi- 
cient to  cause  outbursts  of  lava,  where  the  nature  of  the  mate- 
rial favored  combustion.  The  low  plains,  lakes,  and  bays 
which  separate  the  Sierras  from  the  coast  hills  are  in  a  po- 
sition similar  to  the  shallow  sounds  which  separate  Nantucket, 
Martha's  Vineyard,  and  Long  Island  from  the  inferior  slopes 
of  the  mountains  of  New  England.  Therefore,  while  agreeing 
with  glacialists,  who  believe  that  great  geological  changes  have 
been  wrought  by  ice-sheets  in  Italy  and  New  England,  it  ap- 
pears to  me  that  the  ancient  glaciers  of  the  Sierra  Nevada  have 
accomplished  more  extensive  work,  owing  to  the  Sierras  being 
situated  in  a  more  favorable  position  to  receive  the  humidity 
of  the  ocean. 

Hence,  with  a  low  temperature,  vast  quantities  of  snow  must 
have  collected  on  their  lofty  sides ;  and  at  the  same  time  their 
great  height  and  declivity  would  cause  the  ice  to  move  down 
their  steeps  with  greater  force  than  the  glaciers  which  passed 


67 

over  New  England.  "Writers  who  have  given  the  subject  con- 
siderable study  think  that  the  deep  valleys  of  the  Sierra  Nevada 
were  produced  by  disruptive  rather  than  erosive  agencies. 
This  conclusion  has  been  formed  from  the  lack  of  large  accu- 
mulations of  debris  about  their  lower  extremities,  which  would 
not  be  the  case  if  such  valleys  were  the  result  of  glacial 
erosion.  But,  should  the  coast  ranges  be  attributed  to  glacial 
action,  as  has  been  stated,  we  can  well  account  for  the  debris 
that  should  accumulate  from  the  erosion  of  the  deep  valleys. 

The  only  thing  that  could  prevent  the  ice  from  gathering 
on  the  Sierra  Nevada  range  during  an  ice  period  in  greater 
masses  than  on  any  mountains  in  the  northern  hemisphere 
would  be  the  lack  of  cold;  for,  with  a  low  temperature,  the 
fall  of  snow  would  be  enormous.  This  is  shown  by  the  great 
snow-fall  during  the  short  mild  winters  of  to-day.  Therefore, 
with  ice-sheets  covering  a  large  portion  of  the  lands  of  the 
high  northern  latitudes,  and  with  the  Japanese  current  which 
tempers  the  north  Pacific  waters  made  cold  in  the  manner 
described  in  the  foregoing  pages,  and  while  the  sea  along  the 
north-west  coast  of  America  was  strewn  with  icebergs  launched 
from  Alaska  and  British  Columbia,  it  seems  that  California 
must  also  have  obtained  a  frigid  climate  during  the  ice  age. 
Therefore,  on  account  of  its  exposure  to  the  ocean  winds,  and 
the  consequent  heavy  snow-fall,  the  accumulation  of  ice  on  its 
lands  must  have  been  immense.  For,  when  it  is  considered 
that  the  glaciers  of  North  America  extended  southward  even 
into  the  torrid  zone  sufficient  to  cover  a  large  portion  of  Cen- 
tral America,  it  is  unreasonable  to  suppose  that  any  portion 
of  California  could  escape  being  covered  by  heavy  ice-sheets 
during  the  glacial  epoch.  The  comparatively  scant  fall  of  rain 
and  snow  over  Greenland  is  known  to  form  ice-sheets  hundreds 
of  feet  in  thickness. 

Therefore,  what  must  have  been  the  depth  of  ice  over  the 
high  lands  of  the  Pacific  coast  north  of  California  at  the  cul- 
mination of  a  frigid  period?  The  descriptions  given  by  Dr. 


68 

Dawson  and  others,  of  glacial  phenomena  along  that  coast, 
favor  the  impression  that  an  immense  ice-sheet  at  one  time 
deeply  covered  the  whole  region  from  the  top  of  the  mountain 
range  to  the  ocean. 

Thus  all  the  deep  channels  were  filled  and  all  the  islands 
deeply  overrun  with  ice,  while  the  immense  bergs  launched 
from  the  shore  and  carried  by  the  winds  and  currents  south- 
ward were  probably  not  melted  until  they  reached  the  tropical 
latitudes.  Thus,  when  the  whole  circulation  of  the  Pacific 
waters  are  taken  into  account,  it  will  be  seen  that  their  temper- 
ature during  the  ice  age  must  have  been  considerably  lowered. 
The  movement  of  ice-sheets  on  the  Pacific  slope  was  probably 
local  in  character,  and  not  connected  with  the  movement  of 
ice  on  the  eastern  sides  of  the  mountains. 

From  what  I  have  seen  of  the  vast  territory  lying  between 
the  Sierra  Nevada  and  the  Rocky  Mountains  it  appears  that  it 
obtained  much  heavier  ice-fields  than  generally  supposed.  Pro- 
fessor Geikie  in  his  lectures  says  of  this  region  that  during 
the  glacial  age,  "in  the  Second  Colorado  Canyon,  the  sides 
were  completely  glaciated  from  bottom  to  top.  These  walls 
are  from  800  to  1,000  feet  high,  and  at  the  thickest  point  the 
glacier  was  1,700  feet  thick  " ;  and  he  says  that  "  the  country 
around  Salt  Lake  was  covered  with  ice,  for  the  rocks  about 
there  show  the  action  of  ice,  and  that  the  bones  of  the  musk-ox 
are  found  there."  This  vast  area  of  ancient  ice,  although 
subject  to  little  movement  in  its  interior  basin,  still,  in  what- 
ever movement  it  may  have  had,  must  have  found  its  main 
outlet  through  the  Grand  Canyon  of  the  Colorado. 

For  in  no  other  way  can  we  account  for  the  erosive  forces 
necessary  to  excavate  that  immense  chasm.  Not  even  the 
mighty  torrent  that  carried  off  the  waters  of  the  melting  ice- 
sheets  that  covered  the  interior  portion  of  the  continent  could 
accomplish  work  of  such  magnitude. 

According  to  Professor  Geikie's  observations  the  Second 
Colorado  Canyon  was  filled  with  glaciers  during  the  ice  age. 


69 

Therefore,  it  seems  that  these  glaciers  must  have  flowed  down 
into  the  Grand  Canyon,  and  there  united  with  glaciers  flowing 
from  more  northern  regions. 

An  account  of  a  collecting  expedition  to  Lower  California 
by  G.  Eison,  in  1895,  describes  ancient  moraines  at  the  ex- 
tremity of  the  peninsula  as  being  prominent,  large,  and  steep. 
This  region  lies  under  the  tropic  of  Cancer,  and  8°  south  of 
the  mouth  of  the  Colorado  River  where  it  empties  into  the 
Gulf  of  California.  Hence  it  appears  that  the  temperature 
of  that  portion  of  North  America  during  the  ice  age  was  favor- 
able for  the  great  glacier  of  the  Colorado  Canyon  to  have 
flowed  into  the  Gulf  of  California. 

The  wide,  shallow  basins  of  Utah  and  Nevada  were  filled 
with  the  water  from  the  melting  ice-sheet  on  the  breaking  up 
of  the  ice  period,  and  the  lakes  so  caused  remained  for  a  con- 
siderable time  after  the  disappearance  of  the  ice.  But,  owing 
to  the  great  evaporation  and  light  rain-fall  of  that  region,  the 
lakes  gradually  shrank  away,  the  filling  and  emptying  of  the 
lake  basins  being  governed  by  the  cold  and  mild  epochs. 

The  conglomerate  deposits  in  the  Appalachian  district  of 
North  America  are  known  as  occurring  on  a  large  scale.  Pro- 
fessor Shaler  is  inclined  to  attribute  them  to  glacial  action, 
because  he  knows  of  no  other  force  that  could  bring  together 
such  masses  of  pebbles  from  a  wide-spread  surface.  In  East- 
ern Kentucky  and  East  Tennessee  these  deposits  are  found  to 
be  several  hundred  feet  in  thickness.  Such  accumulations  of 
apparent  glacial  origin  are  to  be  found  from  New  Brunswick 
to  Alabama. 

Hence  it  seems  that  the  ice  during  a  frigid  period  followed 
down  the  Alleghany  range  even  so  far  south  as  Georgia  and 
Alabama ;  and  for  a  time,  when  the  ice  attained  its  greatest 
spread,  it  flowed  over  the  central  portion  of  the  Gulf  States. 
For  how  else  can  we  account  for  the  clay  mixed  with  gravel  and 
pebbles  and  stony  fragments  being  spread  broadcast  over  that 
region  ? 


70 

I  know  that  such  statements  do  not  agree  with  the  views  of 
glacialists  who  have  written  on  the  subject,  and  have  drawn 
the  glacial  boundary  from  seven  to  ten  degrees  further  north, 
where  a  line  of  bowlders  with  other  glacial  debris  is  plainly 
traced.  Still,  it  appears  to  me  that  a  line  of  bowlders  de- 
posited by  an  ice-sheet  spreading  over  a  continent  and  across 
many  degrees  of  latitude  cannot  be  compared  to  the  moraines 
of  inferior  mountain  glaciers  of  the  temperate  latitudes  of  the 
present  age. 

An  ice-sheet  moving  from  a  high  latitude  to  a  lower  would, 
while  in  the  colder  latitude,  freeze  firmly  to  the  rocky  ledges, 
and  hold  them  so  strong  in  its  frigid  grasp  as  to  break  off  the 
weaker  portions  of  the  rocks,  and  drag  them  toward  a  milder 
region,  as  far  as  the  freezing  grip  of  the  ice-sheet  would  per- 
mit ;  but,  on  gaining  lower  and  milder  latitudes,  the  holding 
and  dragging  power  of  the  ice  would  be  lost  on  account  of  the 
increased  warmth  of  the  earth  over  which  the  glacier  must 
pass,  and  also  because  of  the  ice-sheet  having  lost  a  portion  of 
the  low  temperature  acquired  in  the  higher  latitudes.  There- 
fore, on  such  lines  the  bowlders  would  be  released,  while  the 
ice-sheet  would  still  move  on,  although  largely  deprived  of  its 
eroding  power. 

This  is  the  probable  reason  why  a  line  of  glacial  debris, 
largely  composed  of  bowlders,  is  found  to  extend  across  the 
Middle  and  Western  States,  and  so  generally  supposed  to  be 
the  glacial  boundary  of  a  frigid  period.  But  there  is  no  reason 
to  suppose  that  an  ice-sheet,  although  deprived  of  its  eroding 
power,  was  arrested  in  its  southern  movement  on  the  line  of  its 
stony  ddbris,  because  there  could  be  no  sudden  change  of  tem- 
perature in  a  particular  latitude  on  the  eastern  lands  of  North 
America  to  cause  an  abrupt  ending  of  the  ice-sheets.  And 
there  appears  to  be  nothing  to  hinder  the  ice  from  gathering 
and  flowing  over  lands  warm  enough  to  loosen  its  implements 
of  erosion  ;  for  there  is  much  to  show  that  the  ice-sheets  flowed 
much  further  southward,  even  into  the  middle  portion  of  the 


71 

Gulf  States,  and  there  spread  the  clay  mixed  with  gravel  and 
pebbles,  with  now  and  then  a  bowlder,  over  the  land.  The 
scattered  bowlders,  found  in  numerous  instances  many  miles 
south  of  the  bowlder  line,  were  so  deeply  imbedded  in  the  ice- 
sheet  that  they  could  not  be  dropped  on  the  usual  releasing 
ground.  The  ice-sheet,  when  deprived  of  its  rocky,  eroding 
implements,  would,  while  flowing  over  the  land,  leave  few  or 
no  imprints  on  the  rocks ;  but  it  would  probably  move  and 
spread  a  large  amount  of  clay,  gravel,  pebbles,  and  sand  over 
its  wide  course,  especially  if  the  ice  moved  from  a  region 
abounding  with  such  material. 

Should  we  place  the  glacial  boundary  on  the  line  of  the  rocky 
debris,  how  could  we  account  for  the  glaciated  stones  found  on 
the  hills  and  plains  situated  far  southward  of  the  bowlder- 
strewn  regions  of  the  Middle  and  Western  States  ?  The  clay 
mixed  with  gravel  and  sand,  and  spread  so  broadcast  over 
a  large  portion  of  Georgia  and  even  into  Northern  Florida, 
makes  it  appear  that  the  ice  of  a  cold  period  must  have  covered 
that  southern  region. 

Moreover,  it  seems  to  have  been  through  the  great  abrasion 
which  only  ice-sheets  could  perform  that  the  sands  of  the 
Florida  peninsula  were  produced;  for  on  examination  they 
seem  to  have  resulted  from  the  abrasion  and  weathering  of 
crystalline  rocks. 

The  worn  remnants  of  such  rocks  are  now  found  in  the 
southern  Appalachian  range.  In  fact,  the  hills  and  mountains 
of  that  region  at  the  present  time  are  supposed  to  be  a  small 
remnant  of  the  ancient  highlands.  Thus,  on  consideration,  it 
appears  that  the  sands  caused  by  the  action  of  glaciers  were, 
on  the  disappearance  of  ice-sheets,  blown  by  the  strong  north- 
west winds  toward  the  Florida  peninsula  as  fast  as  the  reced- 
ing waters  of  the  ocean  which  flowed  the  lowlands  on  the 
breaking  up  of  the  ice  age  would  permit ;  and  in  this  way  the 
sand  was  spread  over  the  lowland  region,  which  was  largely 
composed  of  coral  sea  shells  and  other  marine  matter.  And  it 


72 

seems  that  the  sand  must  have  been  blown  over  large  areas  in 
Florida  soon  after  the  ending  of  the  frigid  period,  because  the 
sand,  in  order  to  be  moved  by  the  winds,  must  have  spread  over 
a  country  nearly  destitute  of  vegetation ;  and  such  would  be 
the  condition  of  that  region  during  times  which  succeeded  the 
ice  period  and  the  subsequent  brief  flowage  of  the  lowlands  on 
the  ending  of  the  frigid  age,  which  would  not  be  the  case  if 
such  sands  resulted  entirely  from  water  erosion  and  weather- 
ing, because  with  such  a  state  of  things  the  country  would  be 
covered  with  forests  and  grasses,  which  would  prevent  the  sand 
from  being  moved  by  the  winds  to  any  great  extent. 

This  goes  to  show  that  the  region  of  the  Gulf  States  was  so 
much  affected  by  the  cold  of  the  glacial  period,  together  with 
the  submergence  of  the  lowlands  at  its  close,  its  flora  and  also 
its  animals  were  exterminated ;  for  how  else  can  we  account 
for  the  abundant  fossil  remains  of  animals  now  found  buried 
in  the  Florida  sands  ?  It  appears  also  that,  when  Florida  was 
being  covered  with  drifting  sands,  many  of  the  lake  basing  now 
formed  did  not  exist,  as  the  wind-blown  sand  could  not  have 
crossed  a  continuous  chain  of  lakes  like  the  St.  John's  River ; 
and  it  is  an  easy  matter  to-day  to  trace  the  beds  of  the  ancient 
lakes  that  prevented  the  sands  from  drifting  over  certain  lands 
now  nearly  destitute  of  it.  And  it  is  probable  that  the  sea 
flowed  the  lowest  lands  during  the  period  when  the  winds  were 
drifting  the  greater  portion  of  the  sands  over  the  peninsula. 
Therefore,  regions  which  embrace  the  Everglades  and  portions 
of  the  Indian  River  territory  are  quite  free  from  heavy  sand 
deposits,  and  so  also  are  the  extensive  flat  woods  of  the 
peninsula. 

Since  the  sands  blew  over  the  ancient  desert  of  Florida,  many 
lake  basins  have  been  formed  because  of  the  sinking  of  the 
ground.  This  sinking  of  the  ground  is  a  common  occurrence 
in  limestone  regions,  where  a  great  amount  of  material  is 
moved  in  solution,  leaving  caverns  whose  roofs  often  fall  in. 
The  great  amount  of  sand  blown  upon  Florida  caused  the 


73 

marine  strata  to  give  way  in  the  weaker  places  under  its 
burden.  The  sinks  thus  formed,  probably  of  frequent  occur- 
rence at  one  time,  have  now  nearly  ceased.  Still,  there  are 
depressions  to  be  seen  to-day  where  the  tops  of  large  pine-trees, 
which  grew  on  dry,  sandy  land,  are  barely  above  the  surface  of 
the  water  which  partly  fills  the  basins  so  recently  formed.  Yet 
I  would  not  assert  that  all  of  the  depressions  where  Florida 
lakes  exist  were  caused  by  the  sinking  of  the  ground ;  for  the 
winds  may  have  caused  shallow  basins  in  the  sand,  where  the 
decayed  vegetation  has  formed  mud  sufficient  to  hold  the  water 
which  now  partly  fills  such  basins. 

The  mobility  of  Florida  sands  can  be  seen  to  good  advantage 
when  exposed  to  a  strong,  dry  north-west  wind,  where  the 
ground  happens  to  be  destitute  of  vegetation.  An  observer  can 
then  realize  what  the  result  would  be,  should  the  whole  land 
be  deprived  of  vegetation  and  laid  bare  to  the  action  of  the 
winds. 

Under  such  conditions,  not  only  would  the  winds  be  much 
stronger  than  now,  but  the  air  near  the  ground  would  be  filled 
with  sand,  moving  like  drifting  snow  in  a  Dakota  blizzard.  And, 
furthermore,  it  is  probable  that  the  rainfall  was  very  light 
while  Florida  was  void  of  vegetation  ;  and,  even  if  shallow 
basins  were  formed,  there  would  be  a  lack  of  rain  to  supply 
them  with  water. 

The  wide  plains  west  of  the  Mississippi  River,  extending 
southward  into  Texas,  during  the  frigid  period  must  have  been 
covered  with  a  sheet  of  ice  and  snow.  And  it  is  probable  that 
it  was  not  wholly  a  product  of  more  northern  latitudes,  but 
was  mostly  produced  by  the  snow  which  fell  on  the  plains 
during  the  long  winters  of  that  period,  which  could  not  be 
melted  away  during  the  cold  summers  of  an  ice  age,  when  it  is 
considered  that  an  ice-sheet,  with  a  temperature  sufficiently  low 
as  to  carry  glacial  drift,  covered  the  lands  of  Missouri  as  far  as 
latitude  38°  south ;  and  it  may  have  been  through  the  pressure 
from  an  ice-sheet  in  its  south-eastern  movement  that  we  are  to 


74 

account  for  the  numerous  ore-bearing  faulting  fissures  travers- 
ing the  limestone  strata. 

The  ice-sheet  was  also  the  probable  cause  of  the  erosion  of 
the  horizontal  bedded  stones,  yet  it  appears  that  the  ice  did 
not  greatly  change  the  contour  of  the  ground;  for  it  is  well 
known  that  glaciers  do  move  over  lands  that  are  not  frozen  to 
the  ice  without  causing  much  disturbance,  especially  where  the 
gradient  is  small,  and  this  was  the  probable  condition  of  the 
Western  plains  during  the  ice  age.  Thus  it  seems  that  what- 
ever disturbance  this  region  has  undergone  could  be  partly 
attributed  to  ice-sheets  without  the  presence  of  bowlder  drift, 
because  the  temperature  and  texture  of  the  ground  in  the  lime- 
stone region  were  unfavorable  for  such  accumulations ;  yet  it 
may  be  owing  to  the  action  of  ice  that  minerals  once  diffused 
are  now  found  collected  in  fissures.  The  deep  valleys  through 
which  the  large  rivers  now  pass  on  their  way  toward  the  sea 
were  once  filled  with  glaciers  which  flowed  into  them  from 
their  tributaries.  Thus  the  deep  trenches  of  the  plains  are 
largely  the  work  of  glaciers.  It  is  generally  supposed  that 
the  driftless  region  of  Wisconsin  was  free  from  ice  during  the 
frigid  period.  But  it  seems  impossible  for  this  region  to  have 
escaped  being  covered  by  ice  and  snow,  with  the  great  lakes 
filled  with  glaciers,  and  the  regions  on  all  sides  of  the  driftless 
area  covered  with  ice. 

The  reason  why  this  territory  escaped  the  drift  from  the 
north  was  on  account  of  the  hindrance  which  the  drift-bearing 
ice-sheet  encountered  in  the  deep  basin  of  Lake  Superior.  In 
this  great  depression  the  ice-sheet  from  the  north  was  relieved 
of  bowlders  and  other  glacial  drift,  as  well  as  obstructed  in  its 
southern  movement. 

Therefore,  the  snow  and  ice  which  gathered  on  the  driftless 
region  had  little  movement  in  any  direction,  while  the  temper- 
ature and  consistency  of  the  ground  under  the  ice  were  not 
favorable  for  the  production  of  bowlder  drift ;  and,  when  we 
consider  that  the  Mississippi  valley  was  deprived  of  great 


75 

sources  of  warmth  during  the  culmination  of  a  glacial  period, 
we  are  forced  to  the  conclusion  that  its  wide  lands  were  also 
covered  with  snow  and  ice. 

The  tropical  waters  of  the  North  Atlantic  were  so  much 
chilled  by  the  floating  icebergs  of  North-eastern  America, 
Greenland,  Iceland,  and  Northern  Europe  that  the  Caribbean 
Sea,  its  warmest  reservoir,  was  reduced  to  a  temperature  so 
low  that  the  easterly  winds  which  blew  over  its  waters  were 
unable  to  prevent  ice-sheets  from  gathering  on  Eastern  Nica- 
ragua. 

Therefore,  during  such  frigid  times  it  appears  that,  with  the 
waters  of  the  Caribbean  Sea  and  Gulf  of  Mexico  reduced  to  a 
low  temperature,  it  was  impossible  for  the  great  Mississippi 
valley  to  escape  glaciation,  while  being  surrounded  by  cold  seas 
and  glaciated  lands  which  extended  even  into  the  tropical  lati- 
tudes. The  broad,  level  lands  of  British  America  and  Siberia 
during  the  ice  age  must  have  been  thickly  covered  by  the  snow 
which  fell  on  the  deeply  frozen  plains,  besides  the  large  amount 
of  snow  that  the  cold  westerly  winds  must  have  drifted  over 
their  icy  surface  from  lands  of  greater  snow-fall  on  their  western 
borders.  This  snow  during  such  freezing  times  could  not  be 
melted  away. 

The  great  ice-sheets  thus  formed  over  wide,  level  lands  could 
have  but  little  motion  in  any  direction,  certainly  not  sufficient 
to  cause  glacial  drift  of  much  magnitude ;  yet  the  ice-sheet,  at 
one  stage  of  its  existence,  probably  served  to  widen  and  deepen 
the  channels  of  the  great  rivers  which  empty  into  the  Arctic 
Ocean  from  these  vast  regions,  and  the  glacial  debris  from  such 
erosion  was  deposited  in  the  arctic  seas. 


76 


CHAPTER  V. 

REMARKS   ON   THEORIES   ADVANCED    FOR   EXPLAINING   ICE 
PERIODS. 

ON  Nov.  12,  1891,  Professor  Geikie  made  his  presidential 
address  before  the  Edinburgh  Geological  Society,  the  subject 
being  "  Supposed  Causes  of  the  Glacial  Period." 

Many  of  his  views  advanced  in  this  lecture  were  so  much  in 
accordance  with  my  own  that  I  am  induced  to  repeat  them. 
He  safd  that  the  glacial  period  was  a  general  phenomenon  due 
to  some  widely  acting  cause,  and  that  where  we  now  have  the 
greatest  rain-fall  the  greatest  snow-fall  took  place,  and  that  the 
Pleistocene  period  was  characterized  by  great  oscillations  of 
climate,  extremely  cold  and  very  genial  conditions  alternating. 
He  also  said  that  in  glacial  and  post-glacial  times  changes  in 
the  relative  level  of  the  land  and  sea  had  taken  place,  and  any 
suggested  explanation  which  did  not  fully  account  for  these 
various  climatic  and  geographical  conditions  could  not  be  satis- 
factory. And,  while  examining  the  earth-movement  hypoth- 
esis, he  pointed  out  that  in  the  first  place  there  was  not  the 
least  evidence  of  great  continental  elevations  and  depressions 
in  the  northern  hemisphere,  such  as  the  hypothesis  postulated. 
Next  he  showed  that,  even  if  the  diserrated  earth-movements 
were  admitted,  they  would  not  account  for  the  phenomena. 

Such  changes,  no  doubt,  would  profoundly  affect  the  maritime 
regions  of  North  America  and  Europe;  but  they  would  not 
bring  about  the  conditions  that  obtained  at  the  climax  of  the 
ice  age. 

Another  objection  to  the  earth-movement  hypothesis  was 
this :  it  did  not  account  for  interglacial  conditions.  The  advo- 
cates of  that  hypothesis  imagined  that  these  conditions  would 
supervene  when  the  highly  elevated  northern  regions  were  de- 
pressed to  their  present  level.  But  these  were  the  conditions 


77 

that  obtained  at  the  present  time ;  and  yet  in  spite  of  them  the 
climate  was  neither  so  equable  nor  so  genial  as  that  which  ob- 
tained in  interglacial  times  and  during  the  mild  stage  of  the 
necessary  post-glacial  period. 

Therefore,  he  said  that  the  earth-movement  hypothesis  should 
be  rejected,  not  only  because  it  was  highly  improbable  that  such 
wonderfully  rhythmic  elevations  and  depressions  of  northern 
lands  could  have  taken  place,  but  chiefly  because  it  did  not 
explain  the  conditions  of  the  glacial  periods  and  interglacial 
times. 

Still,  Professor  Geikie  says  that  in  glacial  and  in  post-glacial 
times  changes  in  the  relative  level  of  the  land  and  sea  had  taken 
place ;  and  it  is  reasonable  to  suppose  that  such  changes  were 
obtained  in  the  high  latitudes  of  both  hemispheres  during  the 
breaking  up  of  the  last  ice  age. 

We  have  previously  pointed  out  that  much  of  the  ice  of  the 
glacial  period  in  the  southern  hemisphere  was  melted  away, 
and  its  waters  warmed  sufficiently  to  assist  the  Gulf  Stream 
and  Japanese  current  to  bring  about  a  mild  period  in  the  north- 
ern hemisphere;  for  without  such  assistance  they  would  be 
unable  to  disperse  the  vast  ice-sheets  of  the  northern  latitudes. 

Still,  the  attraction  of  the  southern  ocean  waters  into  the 
northern  seas  must  have  commenced  as  soon  as  the  growing 
ice-sheets  of  the  large  continents  and  islands  of  the  high  north- 
ern latitudes  surpassed  the  growth  and  weight  of  the  glaciers 
on  the  smaller  lands  of  the  southern  hemisphere. 

Hence  the  attraction  of  the  ocean  waters  northward  over- 
comes the  force  of  the  prevailing  winds  from  moving  an  undue 
portion  of  the  ocean's  surface  waters  southward.  Consequently, 
the  movement  of  water  from  the  southern  seas  into  the  northern 
latitudes  continued  so  long  as  the  vast  northern  ice- sheets  in- 
creased in  weight  greater  than  the  glaciers  of  the  southern 
hemisphere.  Therefore,  at  the  perfection  of  a  frigid  age  straits 
and  channels  situated  so  far  southward  as  the  Magellan  and 
Cape  Horn  channels  were  much  diminished  in  width  and  depth 


78 

or  entirely  deprived  of  their  waters.  Through  this  cause  such 
reduced  channels  were  readily  filled  with  glaciers  in  a  region  of 
great  snow-fall.  The  depth  of  water  on  the  submerged  northern 
lands  at  the  close  of  the  glacial  period  is  not  known. 

According  to  Professor  Dawson,  in  the  township  of  Montague 
in  Ontario  the  skeleton  of  a  whale  was  found  in  post-glacial 
deposits  440  feet  above  tide-water,  and  marine  shells  are 
known  to  occur  on  Montreal  mountain  at  an  elevation  of  520 
feet  above  the  ocean ;  and  it  is  said  that  there  are  traces  of 
submergence  of  over  one  thousand  feet  in  the  higher  latitudes, 
including  the  islands  of  Great  Britain. 

According  to  the  researches  of  Dr.  J.  W.  Spencer,  one  great 
sheet  of  water  covered  most  of  the  great  lake  region  about  the 
close  of  the  ice  age;  and  the  lower  strands  of  these  inland 
seas  are  known  to  be  connected  with  old  marine  shore  lines. 
The  probable  reason  why  so  few  sea-shells  collected  on  the 
glacial  drift  during  such  times  was  because  of  so  much  marine 
life  having  been  exterminated  in  the  high  northern  latitudes 
during  the  frigid  age.  Therefore,  the  sea,  in  the  short  period 
of  northern  submergence,  left  but  few  traces  on  the  glacial 
drift  it  once  flowed. 

Thus  it  will  be  seen  that,  if  the  ocean  waters  were  attracted 
northward  through  the  preponderance  of  northern  ice-sheets, 
they  not  only  assisted  in  melting  the  northern  ice,  but  also 
served  to  greatly  reduce  the  waters  in  the  Cape  Horn  channel, 
and  so  largely  prevented  the  independent  circulation  of  the 
southern  ocean,  thus  furthering  a  mild  climate  in  the  southern 
hemisphere  until  the  prevailing  winds,  after  the  northern  ice- 
sheets  were  melted,  were  able  to  move  more  of  the  ocean  waters 
southward  than  they  could  move  northward,  owing  to  the  ocean 
currents  setting  southward  being  less  obstructed  than  the  lesser 
currents  setting  northward.  This  tendency  of  the  ocean  waters 
to  move  southward  I  have  before  explained  in  the  preceding 
pages. 

But  I  will  say  in  addition  that,  on  further  consideration,  it 


79 

seems  that  one  of  the  main  causes  of  the  waters  of  the  aug- 
mented northern  oceans  moving  southward  so  soon  after  the 
melting  of  the  ice  from  the  northern  lands  was  on  account 
of  so  much  water  being  attracted  southward  to  the  great  low 
sea-level  east  of  Cape  Horn.  This  vast  low  sea-level  remained 
a  great  area  of  attraction  for  the  northern  seas  until  so  much 
northern  water  was  moved  into  the  southern  ocean  as  to  reduce 
the  seas  of  the  northern  hemisphere  and  augment  the  southern 
ocean  sufficiently  to  enlarge  the  Cape  Horn  channel,  thus  caus- 
ing the  extinction  of  the  vast  low  sea-level  that  furnished  such 
great  attraction  for  the  waters  of  the  more  northern  latitudes. 

If  the  earth-movement  hypothesis,  so  wholly  rejected  by  Pro- 
fessor Geikie,  fails  to  explain  the  cause  or  causes  of  a  northern 
ice  age,  it  seems  to  be  still  more  inadequate  for  explaining  the 
occurrence  of  ice  periods  extending  over  both  hemispheres. 
For  it  is  not  probable  that  portions  of  continents  and  large 
islands  rose  above  the  snow-line  in  both  temperate  zones  during 
the  same  period  of  time,  and  then  again  obtained  their  present 
level  with  the  occurrence  of  a  mild  era. 

Those  who  maintain  that  the  continents  of  North  America 
and  Europe  rose  to  great  elevations  during  the  ice  age,  in  order 
to  prove  their  assertions,  point  to  the  fiords  which  indent  the  east- 
ern and  western  coasts  of  North  America,  and  also  to  the  fiords 
of  Norway,  as  having  been  eroded  by  streams  of  ice  that  flowed 
along  the  bottom  of  such  gorges  when  they  were  above  the  sea. 

But  it  appears  that  such  erosion  could  be  performed  by  heavy 
glaciers  with  the  lands  at  their  present  level.  A  glacier  three 
thousand  feet  thick  would  fill  and  press  heavily  on  the  bottom 
of  a  gorge  fifteen  hundred  feet  in  depth.  Therefore,  should 
the  bottom  of  a  fiord  sink  hundreds  of  feet  below  the  sea-level, 
a  glacier  several  thousand  feet  thick  flowing  through  and  over 
it  into  a  sea  of  much  greater  depth,  the  erosion  at  the  bottom 
of  the  sunken  channel  would  be  greater  than  on  the  land  above 
the  sea,  where  the  ice  possessed  less  weight. 

Therefore,  it  is  not  necessary  that  lauds  pierced  by  deep 


80 

fiords  should  have  acquired  a  higher  level  during  the  ice  age 
than  they  now  maintain.  And  it  is  probable  that  on  the  ant- 
arctic continent  ice  erosion  may  be  going  on  at  much  greater 
depths  below  the  sea-level  than  the  deepest  channels  in  the 
high  northern  latitudes.  For  it  is  likely  that  the  temperature 
of  a  glacier  is  so  low  in  such  frigid  regions  that  it  holds  firmly 
in  its  freezing  grasp  such  bowlders  as  may  become  detached 
from  the  rocks,  thus  giving  it  great  erosive  power. 

But  this  great  eroding  ability  could  not  be  maintained  by 
glaciers  in  the  lower  latitudes,  where  a  higher  temperature 
would  largely  deprive  the  ice  of  its  abrading  properties  except 
on  the  steep  slopes  of  mountainous  lands. 

There  are  deposits  of  ice  on  the  North  American  coast  bor- 
dering the  arctic  shores,  and  also  on  Northern  Siberia,  that  are 
supposed  to  have  existed  since  the  last  frigid  period,  and  are 
likely  to  be  preserved  into  a  future  cold  age,  which  now  appears 
to  have  made  considerable  progress  on  Greenland  and  other 
ice-clad  arctic  shores  on  account  of  the  independent  circulation 
of  the  Arctic  Ocean  waters,  which  largely  excludes  the  Gulf 
Stream  from  the  polar  seas ;  and  it  is  for  this  reason  that  the 
glaciers  on  the  elevated  lands  of  Iceland  are  being  enlarged 
and  rapidly  advancing.  Yet,  notwithstanding  the  gathering  of 
ice  and  increasing  coldness  of  lands  largely  removed  from  the 
warm  Gulf  currents,  there  are  still  mountain  regions  where 
glaciers  may  have  been  preserved  through  post-glacial  times, 
although  directly  to  the  leeward  and  under  the  influence 
of  the  Gulf  Stream  and  Japanese  currents.  These  glaciers  are 
situated  in  the  Alpine  districts  of  Europe  and  on  the  mountain 
ranges  of  Alaska.  It  would  appear  that,  were  the  climate 
growing  gradually  colder  in  the  northern  temperate  zones,  such 
glaciers  should  be  increasing  in  size. 

Yet  it  is  said  that  such  is  not  always  the  case.  This  is  prob- 
ably owing  to  their  being  subject  to  the  genial  influence  of 
the  tropical  currents.  For,  although  the  climate  of  Europe 
and  Alaska  may  have  been  slowly  growing  colder  for  centuries, 


81 

still  the  slow  shrinkage  of  these  once  immense  glaciers  may 
still  be  going  on,  although  at  a  much  slower  rate  than  formerly, 
even  if  the  tender  plants  of  these  latitudes,  because  of  the 
growing  coldness,  have  gradually  moved  southward. 

As  to  the  Alpine  glaciers,  M.  Forel  reports  from  data  he  has 
collected  that  there  have  been  several  enlargements  and  dim- 
inutions during  the  last  century.  And  since  1875  enlargements 
have  taken  place,  their  shrinkage  being  caused  by  warm  and 
dry  weather,  while  their  enlargement  was  brought  about  dur- 
ing cold  and  rainy  seasons.  The  glaciers  of  Alaska  cannot  at- 
tain much  extension  until  the  waters  of  the  great  Japanese 
stream  acquire  a  lower  temperature.  There  is  at  this  date  a 
small  current  setting  down  through  the  eastern  side  of  Bering 
Strait,  bearing  field-ice  in  the  spring  season  down  to  Anadyr 
Gulf.  The  Okhotsk  Sea  in  the  spring  season  furnishes  consid- 
erable field-ice  to  cool  the  north  Pacific  waters,  and  the  wintry 
winds  which  sweep  down  from  the  high  lands  of  Northern  Asia 
also  serve  to  chill  the  Pacific  seas ;  but  all  such  sources  of  cold 
combined  at  this  age  have  but  little  general  effect  on  the  vast 
Japanese  current,  which  still  has  warmth  sufficient  to  prevent 
the  increase  of  glaciers  on  Alaska. 

This  great  ocean  stream  in  its  impact  against  the  shores  of 
Oregon  causes  a  high  sea-level,  which  is  mostly  turned  south- 
ward by  the  prevailing  north-west  winds.  Still,  a  compara- 
tively small  stream  sets  along  the  shore  of  the  Alaska  Gulf,  and 
also  through  the  island  passages  toward  a  slight  low  sea-level, 
to  the  leeward  of  the  Alaska  peninsula ;  and  it  is  probable 
that  this  current  which  warms  these  in-shore  waters  is  favored 
by  the  difference  of  temperature  and  density  between  the 
waters  abreast  Oregon  and  the  Gulf  of  Alaska,  and  it  may  be 
owing  to  the  same  cause  that  a  small  stream  is  sent  along  the 
eastern  shore  of  Bering  Strait  into  the  deep  portions  of  the 
Arctic  Ocean.  Thus  because  of  the  warm  waters  that  proceed 
from  the  great  Japanese  current  the  glaciers  of  Alaska  are 
prevented  from  increasing  their  bulk. 


82 

The  only  way  to  furnish  the  Japanese  stream  with  colder 
water,  and  so  cause  glaciers  to  increase  on  the  north-west  coast 
of  America,  is  through  the  great  Humboldt  current,  which  has 
its  rise  in  the  southern  ocean  west  of  Patagonia  and  the  Cape 
Horn  channel,  where  a  moderate  but  vast  high  sea-level  is 
formed  on  account  of  the  great  drift  current  of  the  southern 
ocean  being  somewhat  obstructed  on  its  passage  through  the 
Cape  Horn  channel,  which  is  about  one-third  the  breadth  of 
the  westerly  wind-belt. 

Therefore,  the  northern  portion  of  the  waters  of  the  high 
sea-level  so  caused  are  attracted  northward  to  the  low  sea-level 
abreast  Peru,  from  whence  they  are  moved  by  the  south-east 
trade  winds  as  a  drift  current  to  the  equatorial  latitudes,  thus 
meeting  and  mingling  with  the  returning  Japanese  current 
abreast  Central  America,  and  so  giving  head  to  the  great 
equatorial  stream  which  moves  westward  over  the  Pacific 
Ocean,  partly  impelled  by  the  trade  winds,  and,  on  gaining 
the  western  side  of  the  ocean,  sends  off  from  a  moderate  high 
sea-level  a  large  stream  to  the  low  sea-level  caused  by  the 
westerly  winds  abreast  Japan,  from  whence  it  is  drifted  by 
the  same  winds  over  to  the  north-west  coast  of  America,  thus 
forming  the  great  Japanese  current. 

Meanwhile  the  temperature  of  the  Humboldt  current,  being 
governed  by  the  temperature  of  the  southern  ocean  from  which 
it  takes  its  rise,  is  cooling  at  a  slow  rate  through  the  enlarge- 
ment of  ice-sheets  in  the  antarctic  regions,  while  the  increase  of 
glaciers  on  Patagonia  will  in  time  greatly  add  to  its  coolness, 
and  so  lower  the  temperature  of  the  equatorial  current  from 
which  the  Japanese  current  branches,  the  latter  current  being 
made  cooler  through  the  increase  of  coldness  of  the  former 
streams.  Therefore,  the  temperature  of  Alaska,  which  is 
governed  by  the  Japanese  current,  will  slowly  acquire  a  colder 
climate ;  and,  consequently,  its  glaciers  will  increase  in  size 
sufficient  to  launch  icebergs  into  the  Pacific  to  be  currented 
southward,  and  so  still  further  lower  the  temperature  of  the 


83 

Eastern  Pacific  waters,  and  consequently  the  equatorial  current 
from  which  the  Japanese  stream  branches,  and  so  eventually, 
under  the  above  conditions,  cause  heavy  ice-sheets  to  spread 
widely  over  the  north-west  coast  of  North  America. 

It  will  be  seen  from  the  above  explanations  how  an  increase 
of  cold  in  the  southern  hemisphere  is  necessary  to  cause  a  wider 
spread  of  ice-sheets  on  lands  in  the  northern  hemisphere. 

Especially  is  this  the  case  to  promote  the  gathering  of 
glaciers  on  the  west  coast  of  North  America.  The  great 
equatorial  current  while  on  its  way  to  the  Indian  Ocean  not 
only  sends  off  the  Japanese  stream,  but  also  the  East  Austral- 
ian current,  which  is  like  the  Japanese  current,  having  its 
temperature  lowered  in  proportion  as  the  equatorial  stream 
is  cooled.  Therefore,  the  southern  ocean  is  slowly  being 
deprived  of  equatorial  heat  from  this  source. 

I  have  explained  how  the  increasing  coldness  of  the  superior 
oceans  of  the  southern  hemisphere  affects  more  or  less  the 
temperature  of  the  Gulf  Stream,  which  meanwhile  is  only  able 
to  enter  a  small  portion  of  its  waters  into  the  Arctic  Ocean 
after  undergoing  a  long  cooling  process  as  a  drift  current; 
and,  while  thus  mingling  with  the  arctic  waters,  it  is  not  able 
to  prevent  the  gathering  of  ice-sheets  on  Greenland,  where 
glaciers  are  launching  bergs  to  float  southward  as  far  as  the 
latitude  of  40°  north.  Consequently,  the  northern  seas  are 
now  being  cooled  as  well  as  the  seas  of  the  southern  hemi- 
sphere. 

Yet  this  cooling  process  is  so  slow  there  is  a  lack  of  data  to 
show  that  the  temperature  of  the  high  latitudes  is  lowering. 
Our  thermometrical  observations  are  of  such  recent  date 
they  cannot  be  used  to  determine  climatic  changes  which  re- 
quires centuries  to  bring  about.  Still,  it  is  generally  known 
that  the  climate  of  Northern  Europe  has  been  accused  of 
growing  colder.  The  vine  no  longer  flourishes  on  the  shores 
of  Bristol  Channel  or  hi  Flanders  or  Brittany ;  and  vineyards 
are  no  longer  planted  on  the  elevated  shores  of  France  where 


84 

they  flourished  three  hundred  years  ago.  Arago  did  not  re- 
fuse to  believe  that  the  laws  regulating  the  temperature  of 
Western  Europe  had  notably  altered.  This  is  proved,  he  said, 
by  the  general  retrogradation  of  the  vineyards  southward. 

The  recent  deadly  freezing  of  the  orange  groves  of  Florida 
makes  it  uncertain  whether  the  cultivation  of  the  orange  can 
again  be  successful  in  the  counties  where  during  this  genera- 
tion it  has  been  very  profitable. 

Travellers  visiting  Iceland  say  that  the  old  accounts  of  its 
prosperity  seem  strange  to  those  who  now  visit  its  shores ; 
and  it  is  narrated  in  the  Sagas  that  in  early  times  sheep  could 
shift  for  themselves  during  winter,  and  that  there  were 
large  forests  and  that  corn  ripened.  Several  years  ago  a  cor- 
respondent of  the  Spectator,  writing  from  Northern  Russia 
where  the  Volga  is  locked  with  ice  for  six  months  in  the  year, 
stated  that  "the  people  were  beginning  to  show  increased  re- 
sentment at  the  climate,  and  that  there  was  reason  to  believe 
that  the  northern  government  of  Russia  would  be  abandoned 
to  the  desert.  The  people  silently  glide  south  by  the  tens  of 
thousands  every  year,  so  the  life  of  Russia  was  concentrating 
in  the  south." 

It  is  now  the  opinion  of  travellers  in  arctic  lands  that  the 
inhabitants  of  the  Esquimaux  regions  are  decreasing,  as  are 
also  the  inhabitants  of  Northern  Siberia. 

A  writer  in  the  North  China  Herald,  of  Shanghai,  says  that 
"  the  climate  of  Asia  is  becoming  colder  than  it  formerly  was, 
and  its  tropical  animals  and  plants  are  retreating  southward 
at  a  slow  rate.  In  the  time  of  Confucius  elephants  were  in  use 
on  the  Yangtse  River.  A  hundred  and  fifty  years  after  this 
Mencius  speaks  of  the  tiger,  the  leopard,  the  rhinoceros,  and 
the  elephant  as  being  in  many  parts  of  China. 

"  It  is  also  said  that  the  ferocious  alligator,  that  formerly  in- 
fested the  rivers  of  South  China,  has  retreated  southward. 

"  The  flora  of  the  country  is  also  affected  by  the  increasing 
coldness  of  the  climate.  The  bamboo  is  not  found  in  the  for- 


85 

ests  of  North  China,  where  it  grew  naturally  two  thousand 
years  ago,  but  is  still  grown  in  Pekin,  with  the  aid  of  good 
shelter,  as  a  sort  of  garden  plant  only." 

A  letter  from  Hong  Kong,  published  in  the  London  Stand- 
ard, reports  that  on  the  15th  of  January,  1893,  the  temperature 
of  Hong  Kong,  a  tropical  seaport  of  China,  was  below  freez- 
ing for  three  days,  and  was  colder  than  ever  before  known. 
The  rocks  and  also  vegetation  were  covered  with  a  coating  of 
ice.  The  thermometer  at  times  stood  at  23°  and  26°  Fahren- 
heit. 

I  have  previously  explained  how  the  slow  increasing  coldness 
of  the  northern  temperate  zone  is  also  being  carried  out  in  the 
southern  hemisphere.  The  meteorological  records  for  the  lofty 
table  lands  of  Ecuador,  although  very  incomplete,  furnish 
strong  evidence  to  show  that  the  mean  temperature  of  that 
region  is  gradually  lowering. 

Observations  made  by  Boussingault  at  Quito  in  1831,  com- 
pared with  those  from  1878  to  1881,  showed  a  decrease  from 
15.2°  Centigrade  to  13.27°  Centigrade. 

Records  made  by  Hall  from  1825  to  1827  give  averages  of 
16.1°  Centigrade,  15.52°  Centigrade,  and  15.6°  Centigrade. 
This  decrease  holds  good  for  all  points  in  the  inter- Andean 
region  where  records  have  been  kept. 

Yet  we  know  that  the  falling  temperature  in  the  northern 
temperate  latitudes  is  not  brought  about  by  a  yearly  increase 
of  cold,  because,  when  the  arctic  channels  are  somewhat  ob- 
structed with  icebergs,  the  movement  of  arctic  waters  through 
them  is  lessened ;  and,  therefore,  during  such  times  the  Gulf 
Stream,  meeting  with  less  opposition  from  arctic  currents  while 
flowing  northward,  is  able  to  move  a  larger  volume  of  its 
waters  into  the  arctic  seas,  thus  warming  their  waters  suffi- 
ciently in  a  few  seasons  to  clear  the  obstructed  channels,  and 
also  somewhat  soften  for  several  successive  years  the  temper- 
ature of  such  lands  as  border  on  the  seas  of  that  region. 

And  in  this  way  we  account  for  the  mild  seasons  which  at 


86 

times  follow  those  of  lower  temperature  in  high  northern  lati- 
tudes. 

But,  when  the  detained  icebergs  are  set  adrift,  and  currented 
into  the  temperate  North  Atlantic,  the  heat  consumed  while 
melting  such  numerous  bodies  of  ice  is  able  to  more  than  over- 
come the  warmth  gained  during  the  temporary  detention  of  ice 
in  the  northern  seas.  Thus,  under  such  considerations,  it  ap- 
pears that  the  conditions  are  favorable  for  the  growth  of  gla- 
ciers in  the  high  northern  latitudes. 

I  have  pointed  out  the  manner  in  which  the  superior  oceans 
in  the  southern  hemisphere  are  obtaining  a  lower  temperature, 
and  how  they  impart  their  coldness  to  the  tropical  currents, 
and  in  this  way  slowly  cool  the  waters  of  all  oceans.  Thus  it 
appears  that  the  northern  temperate  zone,  with  all  other  parts 
of  the  earth,  is  slowly  approaching  a  cold  epoch. 

Several  writers  on  climatic  changes  have  expressed  their 
views  as  to  the  number  of  glacial  and  mild  periods  that  have 
been  perfected  since  the  conditions  have  been  favorable  for 
their  appearance  on  the  globe.  According  to  my  views,  while 
considering  the  reasons  for  the  occurrence  of  the  great  glacial 
periods  which  have  left  such  extensive  traces  on  the  land,  it 
seems  certain  that  two  very  cold  epochs  have  possessed  the 
earth,  separated  by  a  warm  period ;  and,  possibly,  other  pre- 
ceding cold  epochs  of  less  intensity  have  possessed  the  high 
latitudes,  with  intervening  periods  of  mildness.  But  the  earlier 
cold  periods,  if  they  ever  existed,  were  comparatively  short, 
because  the  Cape  Horn  channel  during  such  times  possessed 
less  capacity  than  in  the  later  periods,  and,  therefore,  was  more 
easily  and  quickly  obstructed  by  the  natural  methods  previously 
explained. 

Consequently,  the  independent  circulation  of  the  southern 
ocean  was  sooner  arrested  than  during  the  later  epoch,  when 
the  channel  had  become  enlarged  by  erosion  from  heavy  gla- 
ciers and  icebergs;  and  meanwhile  the  same  conditions  may 
have  governed  the  arctic  channels  which  give  an  independent 


87 

circulation  to  the  arctic  waters  which  surround  Greenland,  and 
thus,  in  connection  with  cold  epochs  in  the  southern  hemisphere, 
have  caused  periods  of  cold  of  small  intensity  to  occur  in  the 
high  northern  latitudes,  and  it  may  happen  in  the  future  that 
more  ice  periods  will  be  perfected  than  the  one  now  progressing. 

Still,  it  is  well  to  bear  in  mind  that  the  Cape  Horn  channel, 
which  is  the  real  cause  of  glacial  periods  having  occurred  in 
both  the  northern  and  southern  hemispheres,  in  the  manner 
previously  explained,  is  being  made  wider  and  deeper  during 
each  succeeding  ice  age.  For  this  reason  the  latest  cold  epoch 
will  require  a  longer  continuance  of  cold  to  obstruct  the  chan- 
nel than  the  cold  period  preceding.  Therefore,  it  appears  that 
the  time  will  come  when  there  will  be  such  great  accumulations 
of  ice  stored  on  the  land  and  in  the  sea  before  the  enlarged 
Cape  Horn  channel  can  be  closed  that,  when  it  is  closed,  there 
will  not  be  sufficient  warmth  remaining  in  the  tropical  seas  to 
unite  with  the  sun's  rays  to  subdue  the  intense  cold  stored  in 
the  immense  gatherings  of  ice.  And  thus  the  earth,  which 
began  its  career  with  a  warm  temperature,  and  so  continued 
for  long  ages,  will  finally  terminate  in  an  endless  glacial  age. 

The  statements  made  by  General  Cowell  in  Science  of  Nov.  25, 
1892,  in  reference  to  the  alleged  discovery  of  the  second  rota- 
tion of  the  earth  by  Major-general  Drayson,  represents  the  dis- 
covery as  affording  a  new  solution  for  the  cause  or  causes  of  an 
ice  age. 

The  second  rotation  as  defined  consists  in  the  pole  of  the 
heavens  describing  a  circle  around  a  point  which  is  ascertained 
to  be  situated  six  degrees  distant  from  the  pole  of  the  ecliptic. 
And  it  is  asserted  that  by  a  knowledge  of  the  second  rotation 
it  is  proved  that  a  variation  of  twelve  degrees  in  the  extent  of 
the  arctic  circle  and  the  tropics  occurred  not  later  than  13,500 
B.C.,  "the  tropics  varying  in  distance  from  the  equator  from 
the  minimum  of  23°  25'  47"  to  the  maximum  of  35°  25'  47", 
thus  extending  the  torrid  zone  during  its  widest  expansion 
from  Cape  Hatteras  to  the  river  Plate.  ...  It  is  calculated  that 


88 

at  this  date  we  are  about  403  years  distant  from  the  time  when 
the  pole  of  the  heavens  in  its  revolution,  the  pole  of  the  ecliptic 
and  that  of  the  second  rotation,  will  be  in  the  same  colure, — 
that  is,  in  the  year  2,295  A.D.  ;  and  then  the  least  differences  in 
temperature  between  summer  and  winter  will  be  experienced. 
From  that  time  forward  this  difference  will  increase,  and  about 
6,000  years  later,  or  about  the  year  8,300  A.D.,  the  earth  will 
enter  the  next  glacial  period,  and  attain  its  greatest  severity 
about  the  year  18,136  of  our  era."  General  Cowell  does  not 
state  how  the  widening  of  the  tropical  zone,  as  above  set  forth, 
would  bring  about  a  glacial  period.  The  winters  of  the  tem- 
perate zones  would  evidently  be  colder  than  now ;  but,  on  the 
other  hand,  the  summers  would  be  proportionally  warmer, 
while  the  westerly  winds  above  the  latitudes  of  40°  would  pre- 
vail the  same  as  now. 

Therefore,  their  general  effect  on  the  surface  waters  of  the 
ocean  in  the  high  latitudes  would  not  be  changed  with  such  an 
extension  of  the  tropical  zone,  neither  would  the  trade  winds 
change  their  general  direction  with  a  wider  torrid  zone ;  yet 
the  boundaries  of  the  trade  winds  and  also  the  westerly  winds 
would  be  more  shifting  according  to  the  declination  of  the  sun, 
such  winds  being  governed  as  now  by  the  position  of  the  sun 
during  the  summer  and  winter  solstice.  Yet  the  natural  proc- 
ess for  moving  tropical  water  into  the  high  latitudes,  or  ex- 
cluding it  therefrom,  would  not  be  greatly  changed. 

Consequently,  the  expansion  of  the  torrid  zone  to  the  latitudes 
named  by  General  Drayson  would  not  affect  the  climate  of  the 
hemispheres  sufficiently  to  cause  a  frigid  epoch.  On  the  con- 
trary, the  summer  monsoons,  which  now  blow  from  the  north- 
east, along  the  shores  of  Eastern  Africa,  and  also  along  the 
coast  of  Southern  Brazil,  would  be  much  stronger  with  a  verti- 
cal sun  in  midsummer  as  far  south  as  river  Plate,  thus  forcing 
the  surface  waters  of  the  tropical  oceans  into  the  higher  lati- 
tudes with  greater  facility  than  at  this  age. 

Moreover,  according  to  the  statements  of  General  Cowell,  the 


89 

present  period  of  mildness  should  be  on  the  increase,  and  obtain 
perfection  in  the  year  2,295,  or  about  400  years  hence;  while, 
on  the  contrary,  according  to  the  explanations  we  have  given 
in  the  preceding  pages,  there  is  much  to  show  that  an  ice  age 
is  advancing,  and  has  made  considerable  progress  in  the  high 
latitudes  of  both  hemispheres.  Furthermore,  if  the  second 
rotation,  as  claimed  by  General  Cowell,  is  able  to  perfect  a 
glacial  period  at  regular  intervals  of  31,600  years,  it  seems  that 
traces  of  frigid  epochs  should  not  be  confined  to  late  geological 
records,  as  there  appear  to  be  little  or  no  traces  of  glacial  work 
prior  to  the  Quaternary  or  Post-tertiary  periods. 

It  appears  that  explanations  so  far  given,  which  depend  on 
the  astronomical  theory  to  account  for  the  ice  age,  are  not  in 
harmony  with  well-known  geographical  facts.  The  explainers 
neglect  the  attention  due  to  the  great  prevailing  winds  which 
since  the  earlier  geological  ages  have,  in  connection  with  conti- 
nents, moved  the  surface  waters  of  the  ocean  from  torrid  lati- 
tudes to  colder  zones,  and  from  the  colder  zones  to  the  warmer 
latitudes. 

This  exchange  of  ocean  waters  between  the  zones  is  as  old 
as  the  continents  which  shape  their  courses.  The  important 
change  wrought  in  the  ocean  currents  sufficient  to  have  caused 
the  glacial  age  which  ended  the  early  warm  epochs  was  brought 
about  through  the  action  of  the  prevailing  winds,  which,  in 
connection  with  the  form  of  continents,  became  able  to  move 
the  ocean  waters  from  the  northern  hemisphere  into  the  south- 
ern sufficient  to  submerge  the  low  lands  of  the  southern  hemi- 
sphere, causing  a  great  diversion  of  the  tropical  currents  from 
the  high  southern  latitudes,  such  as  I  have  pointed  out  in  pre- 
ceding chapters. 

Those  writers  who  believe  that  ocean  currents  have  been  the 
cause  of  great  climatic  changes  have  suggested  that  the  exist- 
ence of  an  ancient  channel  through  the  isthmus  of  Panama 
would  have  caused  a  frigid  period  on  lands  bordering  on  the 
northern  shores  of  the  Atlantic  by  turning  the  head-waters  of 
the  Gulf  Stream  into  the  Pacific  Ocean. 


90 

Professor  Agassiz  thinks  that  such  a  channel  existed  during 
some  remote  geological  age,  judging  from  the  semblance  of  the 
fauna  pertaining  to  the  Caribbean  Sea  and  Pacific  Ocean. 

Yet  it  may  be  said  that  an  open  channel  through  Central 
America  would  have  connected  two  high  sea-levels. 

For  this  reason  there  would  be  little  or  no  exchange  of  water 
between  the  Caribbean  Sea  and  the  Pacific  Ocean. 

The  high  sea-level  on  the  Pacific  side  is  caused  by  the  pre- 
vailing north-west  winds  which  blow  down  the  North  American 
coast  past  California  as  far  south  as  Central  America ;  while, 
on  the  other  hand,  the  south-east  trade  winds  impel  the  surface 
waters  of  the  South  Pacific  along  the  coast  of  Peru  down  to 
the  equator,  and  so  onward  5°  to  8°  north  latitude.  Thus  the 
space  between  the  ending  of  the  two  ocean  winds  obtains  a  high 
sea-level,  corresponding  to  the  high  level  of  the  Caribbean  Sea. 
This  has  been  proved  from  levellings  for  the  Nicaragua  ship 
canal. 

Consequently,  the  Atlantic  waters  would  not  run  into  the 
Pacific  Ocean,  even  if  a  channel  opened  through  Central 
America. 

Therefore,  the  Gulf  Stream  has  never  been  turned  away 
from  the  North  Atlantic. 

Writers,  while  seeking  a  cause  for  the  mild  climate  of  ages 
preceding  the  glacial  epochs,  have  thought  that  during  such 
times  channels  opening  through  Asia  from  the  Indian  Ocean 
by  the  way  of  the  Persian  Gulf  into  the  arctic  seas  would  be 
the  means  of  furnishing  the  Arctic  Ocean  with  warm  water. 
But  it  is  evident  that  such  a  movement  of  water  could  not  be 
brought  about,  because  the  winds  would  not  be  favorable  for 
it.  For,  when  we  reflect  that  the  prevailing  winds  would  blow 
in  the  same  direction  as  now,  and  that  the  seas  of  Eastern  Eu- 
rope and  Western  Asia  were  enlarged  during  the  warm  epochs, 
it  seems  that  they  would  obtain  high  levels  superior  to  the 
high  level  seas  of  the  Indian  Ocean. 

Besides,  we  should  consider  that  there  is  a  continuous  range 


91 

of  high  land  separating  the  Persian  Gulf  from  the  northern 
seas,  which  probably  existed  anterior  to  the  ice  age.  Still, 
during  later  periods,  while  the  ice-sheets  were  being  melted 
from  the  northern  hemisphere  and  also  on  the  ending  of  the 
last  ice  age,  the  Isthmus  of  Suez  was  submerged,  as  were  all 
other  low  lands  in  that  latitude;  but  it  is  probable  that  the 
waters  of  the  high  sea-level  of  the  Indian  Ocean  abreast  tropi- 
cal Africa  did  not  flow  largely  into  the  Mediterranean  Sea  for 
the  reason  that  the  enlarged  European  seas,  being  within  the 
westerly  wind-belt,  maintained  a  high  sea-level,  while  at  the 
same  time  the  high  level  tropical  Indian  Ocean  waters  were 
strongly  attracted  into  the  southern  oceans  through  the  Mo- 
zambique and  Agulhas  currents  in  the  manner  I  have  pre- 
viously explained.  Yet  the  waters  of  the  high  sea-level  of  the 
southern  European  seas  must  have  been  strongly  attracted  to 
the  low  sea-level  abreast  the  Canary  Islands. 

While  considering  the  causes  which  brought  about  the 
glacial  periods,  it  is  well  to  reflect  that  the  natural  mode  of 
action  which  could  have  produced  a  frigid  age  was  as  exten- 
sive as  the  surface  of  the  globe ;  and,  therefore,  any  geographi- 
cal change  that  would  affect  only  a  comparatively  small  por- 
tion of  the  earth  cannot  serve  to  account  for  ages  of  warmth 
which  extended  over  the  globe,  or  for  glacial  epochs  which 
were  separated  by  warm  periods  of  time,  which  seem  to  have 
affected  all  lands  and  seas. 

And  it  appears  from  the  geographical  explanations  given  in 
preceding  pages  of  the  general  movements  of  the  winds  and 
currents  of  the  sea  how  impossible  it  is  for  heat  to  be  con- 
veyed to  the  antarctic  latitudes  sufficient  to  prevent  the  growth 
of  glaciers  on  their  lands  while  the  Cape  Horn  channel  is  in 
possession  of  its  present  capacity. 

For,  as  has  been  shown,  this  channel  furnishes  opportunity 
for  the  westerly  winds  to  impel  the  surface  waters  of  the  great 
southern  ocean  constantly  around  the  globe,  and  so  largely 
turns  away  the  tropical  currents  from  the  high  southern  lati- 
tudes. 


92 

Consequently,  there  seems  to  be  no  method  yet  devised 
through  nature's  mode  of  action  that  can  carry  sufficient  heat 
into  the  antarctic  latitudes  to  melt  the  ice-sheets  from  the 
southern  continent,  or  even  arrest  their  growth,  while  the  Cape 
Horn  channel  maintains  its  present  width  and  depth. 

Therefore,  the  increase  of  glaciers  and  icebergs  will  slowly 
continue  until  a  glacial  epoch  is  perfected. 

And  it  seems  that  this  arrangement  for  bringing  about  a 
frigid  age  made  slower  progress  in  its  early  stage  than  at  this 
date,  owing  to  there  having  been  a  lack  of  glacial  ice  in  the 
polar  regions  to  produce  icebergs  for  cooling  the  ocean  waters. 
But  the  independent  circulation  of  the  great  southern  ocean, 
after  turning  away  the  tropical  currents  from  the  high  southern 
latitudes  for  thousands  of  years,  did  at  length  cause  glaciers  to 
form  on  the  antarctic  lands,  which  have  been  slowly,  but  con- 
stantly increasing ;  and,  consequently,  the  cooling  of  the  ocean 
has  been  accelerated  proportionate  to  the  increase  of  ice-sheets. 
Therefore,  with  the  cooling  process  so  well  advanced  as  it  now 
appears  to  be,  it  seems  that  more  than  half  of  the  time  required 
to  bring  a  frigid  age  to  perfection  has  been  expended  since  ice- 
sheets  began  to  gather  on  the  antarctic  shores.  For,  when  we 
realize  how  the  facilities  for  making  ice  have  advanced  through 
the  increase  of  glaciers  in  both  hemispheres,  and  how  large  a 
portion  of  the  ocean  waters  have  been  cooled  below  a  temperate 
or  tropical  temperature  even  in  the  torrid  latitudes  where  the 
warm  upper  waters  of  the  ocean  have  been  reduced  to  a  com- 
paratively thin  stratum  when  compared  to  the  vast  bulk  of 
the  cooled  under  waters,  it  appears  that  the  cold  will  increase 
at  a  faster  rate  for  the  next  thousand  years  than  was  the  case 
during  the  last  ten  centuries.  Therefore,  the  climate  will  be 
less  favorable  for  plants  and  animals  existing  on  lands  in  the 
high  latitudes  for  the  next  thousand  years  than  during  the  ten 
centuries  preceding;  and,  when  we  take  into  consideration 
the  accelerative  growth  of  a  frigid  epoch,  it  seems  that  the  in- 
creasing cold  will  in  a  few  thousand  years  drive  the  greater 


93 

portion  of  both  plants  and  animals  from  the  now  temperate 
latitudes  to  maintain  an  existence  in  the  tropical  zone,  where  a 
large  part  of  the  existing  species  of  such  life  must  have  taken 
refuge  during  the  last  ice  period. 

And,  from  what  can  be  learned  from  the  relics  of  man's  pre- 
historic life,  it  seems  to  point  to  the  lands  of  the  tropical  lati- 
tudes as  having  been  his  home  during  the  frigid  ages ;  and, 
because  of  his  long  undisturbed  residence  in  favored  portions 
of  the  tropics,  he  there  attained  his  earliest  civilization.  For  it 
appears  that  the  tropical  zone  was  not  only  less  burdened  with 
ice  in  glacial  times  than  the  higher  latitudes  of  the  globe,  but 
was  also  more  exempt  from  the  great  flooding  of  lands  which 
obtained  in  the  more  northern  latitudes  through  the  shifting  of 
the  ocean  waters,  from  causes  set  forth  in  the  preceding  pages. 
Yet  it  may  be  said  that  the  low  lands  of  the  tropical  zone 
south  of  the  equator  during  cold  epochs  were  much  more  ex- 
tensive than  at  this  age,  on  account  of  the  shrinkage  of  the  sea, 
because  of  the  great  amount  of  water  evaporated  from  its  sur- 
face, and  stored  in  ice-sheets  on  the  great  continents  and 
islands.  Hence  the  reefs  and  shallows  which  surround  such 
tropical  islands  as  include  the  Seychelles  Archipelago,  and  also 
the  extensive  banks  covered  with  shoal  water  in  that  portion  of 
the  Indian  Ocean,  were  during  the  glacial  period  elevated  above 
the  surface  of  the  sea,  possessing  a  climate  favorable  for 
vegetable  and  animal  life.  But,  owing  to  the  great  rain-fall  of 
that  region,  it  is  probable  that  the  highest  lands  were  glaciated, 
as  it  is  reported  that  granite  bowlders  still  rest  on  the  moun- 
tain slopes  of  the  highest  island.  The  numerous  islands  and 
shoals  of  the  south-western  tropical  Pacific  must ;  also  have 
afforded  wide  land  areas,  with  a  temperate  climate,  owing  to 
their  having  been  situated  on  one  of  the  warmest  regions  of 
the  earth  during  the  ice  age. 

Moreover,  it  is  probable  that  these  tropical  lands  afforded 
space  for  numerous  lagoons  which  had  little  connection  with 
the  surrounding  oceans,  and  consequently  were  able  to  main- 


94 

tain,  in  their  secluded  shallow  basins,  a  warmer  temperature 
than  obtained  in  the  open  seas ;  and  at  the  same  time,  owing 
to  the  great  rainfall  in  such  tropicalfportions  of  the  Indian  and 
Pacific  regions,  the  waters  of  the  lagoons  were  rendered  less 
salt  than  the  briny  depths  of  the  shrunken  oceans  of  a  cold 
period.  Hence  because  of  such  conditions  the  fauna  of  the 
tropical  seas  were  preserved  from  the  destructive  rigor  which 
beset  the  earth  during  the  frigid  epochs. 


*'*"• 

This  book  is  DUE  on  the  last 
date  stamped  below 


*  t*L^.  &**     'is**-  -  ^  ££>  -^ 


&> 

>m  L 

'^«^%^^^|j;^ 


' 


